The day after President Reagan was shot, his top aides put out the word that it would be "business as usual" at the White House during Reagan's hospitalization and recuperation.

Dr. Dennis O'Leary of George Washington University Hospital was equally quick to describe Reagan's recovery from a bullet in his lung and chest surgery as "super" and "remarkable."

Amid the euphoria resulting from the fact that the would-be assassin's bullet had not done more damage -- and fueled by the president's gallant, wisecracking approach to his injury -- great expectations were born that Reagan, despite his 70 years and regardless of the gravity of his wound, would be back in the Oval Office in record time.

The 11 days since Reagan returned to the White House from the hospital have made clear, however, that it is not "business as usual" and that the president had needed more time to recuperate than some of his aides first hoped.

Reagan put the image and the reality succinctly himself on the day he left the hospital. How do you feel? reporters called out. "Great," Reagan replied in his role as keeper of the image and reassurer of the nation.

What are you going to do when you get home?

"Sit down," the president said.

Reagan's advisers describe themselves as trying to steer a course between two dangers during these first weeks after the assassination attempt.

One danger is that the White House would be perceived as running smoothly in the absence of the president, leaving the administration open to criticism that Reagan's trio of senior aides, counselor Edwin Meese III, chief of staff James A. Baker III and deputy chief of staff Michael K. Deaver, are running the country, with the implication that the president is not vital to the running of his government.

Equally dangerous would be the perception that "we've got a sick, old man up there," one adviser said.

Under pressure to chart this course without unduly pushing the president before he regains his full strength, White House officials yesterday allowed reporters to interview Reagan for the first time since the shooting.

However, instead of a full news conference, only reporters and photographers, from the two major U.S. news services, Associated Press and United Press International, were taken to see Reagan, and they were asked to confine questions to the assissination attempt and the president's health.

The decision to hold even this limited meeting with reporters and how to arrange it was made after thorough discussion among senior White House aides.

Also under discussion is how best to arrange the president's public appearance as he gradually emerges from his convalescence.

Reagan and his advisers expect heightened interest in his first several appearances, enabling them to keep the spotlight on the economic program that is nearing crucial congressional voting tests.

Just as Reagan held the spotlight with ease in the first weeks after his inauguraition, White House officials expect he once again will be the focus of intense curiosity and will benefit from public sympathy about his injury.

The president will make a televised address in support of his package of tax and spending cuts, probably next week so it would be close to the House vote on the budget proposal drafted by Reps. Phil Gramm (D-Tex.) and Delbert L. Latta (R-Ohio) and endorsed by Reagan.

A victory on that vote in the Democratic-controlled House would be an enormous psycholgical lift for the Reagan administration, White House aides say, and could establish a tone that would make it easier to win later House votes.

After the television speech, Reagan's first trip outside Washington is scheduled to come May 17, when he plans to speak at the University of Notre Dame commencement in South Bend, Ind.

Reagan's injury came just before the lull that always accompanies a congressional recess. The recess, which began April 10 and is to end Monday, has worked in Reagan's favor since fewer demands would have been made on him at this time anyway, but the lull also has highlighted the absence of activity at the White House.

"Actually, I don't think I'd be doing anything different," Reagan told his interviewers yesterday. However, before the shooting, Reagan was meeting groups of people regularly in the Oval Office, and his activities dominated the news.

Relatively short workdays have always been a Reagan hallmark. To critics who accuse him of being lazy, he has replied: "Show me an executive who works long, long hours, and I'll show you a bad executive."

Deputy press secretary Larry Speakers says Reagan now is working four or five hours a day. Before he was shot, he worked fewer hours some days, particularly Wednesdays when he liked to have the afternoons free.

Then, Reagan was usually working about an eight-hour day and chairing numerous meetings. Now, he spends all of his time in the White House living quarters and sees very few people, maintaining regular contact only with Meese, Baker and Deaver.

The president is expected to make his first post-shooting visit to the Oval Office next week, but so many predictions have slipped that forecasts are now hedged.

"It's just as if the president were here in the Oval Office, the way the White House is running," Deaver said the day after the shooting.

O'Leary first predicted that Reagan would leave the hospital April 6 or 7. He left April 11.

Baker said April 6 that he hoped Reagan could make a television or radio speech April 15 on his tax cut plan.

On April 10, O'Leary predicted that Reagan probably would be working in the Oval Office for half of every day beginning this week.

By all accounts, the president is making an excellent recovery for a 70-year-old who suffered a serious gunshot wound. The comeback is just taking more time than some first thought it would.