When President Carter sent Congress his moderately tight fiscal 1980 budget in January, he admonished the lawmakers to hold spending down sharply enough to limit the deficit to $29 billion.

Any more than that, Carter warned, would worsen inflation.

Today, House-Senate conferees are scheduled to begin work on a compromise congressional budget resolution that not only would meet Carter's target but probably go him a few billion dollars better.

What's more, most of the president's spending proposals for individual programs probably will remain virtually intact. In effect, the president has won a victory in the budget battle this year.

It may not seem that way at first glance-at least, not from the purely numerical targets that the two houses have voted over the past four weeks, both for overall spending levels and for specific categories.

The House has approved a deficit of $20.9 billion, a full $7.5 billion below the revised $28.4 billion deficit Carter has proposed. And it called for spending of $529.9 billion, compared with Carter's $532.3 billion.

The Senate called for a deficit of $29 billion, with spending at $532.6 billion. But its figures were based on more pessimistic economic predictions. Using Carter's projections, the Senate's deficit would be $19.9 billion.

Actually, however, both congressional and White House budget analysts say there's less to those apparent disparities than meets the eye, particularly in how much they change Carter's proposals for individual programs.

Most of the congressional reductions in Carter's proposed deficit represent more bearish economic assumptions and "technical" re-estimates. These account for $5.5 billion of the $7.5 billion House reduction, and $5.9 billion of the more complex Senate estimates.

Other differences hinge on the way in which the two houses calculated the impact of proposed changes in tax laws.

For example, both houses killed Carter's proposal for "real wage insurance," but differed over how much that would save in figuring the deficit. The House used Carter's $2.3 billion estimate. The Senate used $5.6 billion.

And the House reduced its deficit estimate artificially by budgeting $1.2 billion more in revenues for repealing the foreign tax credit for oil companies, if such a measure ever passes, it would pick up only $300 million.

Perhaps the most sweeping change from Carter's budget was a last-minute House measure that would trim an extra half percentage-point from spending in all programs. But even here, the cuts, in most cases, would be small.

All sides agree that the two houses have made few serious cutbacks in the spending levels Carter proposed for most major programs. And those differences are likely to be pared further when the compromise emerges from conference.

Moreover, no matter what ecomonic assumption the various budgetmakers say they use, the actual numerical targets become the ceilings. A compromise spending limit of, say, $531.3 billion would be just under Carter's.

Apart from the last-minute House proposal to cut spending another half percentage-point-which isn't likely to pass in conference-Carter's fiscal 1980 defense spending plan remained virtually unscathed.

Although the House slashed $3.1 billion in Pentagon authority to begin new long-term projects, it trimmed only $400 million in actual fiscal 1980 spending-out of a $126 billion budget. The Senate left Carter's figure virtually intact.

The lawmakers' most controversial cut in social programs also was largely symbolic. The Senate voted to reduce the anti-recession portion of the public-service jobs program to 100,000 slots by the end of fiscal 1980, instead of 200,000.

But the difference involves a dispute over how many jobs are being financed now, and may not mean much in reality. (The House voted to approve Carter's figures and add some extra for summer youth programs.)

Other key differences:

Urban initiative: Both houses approved Carter's revised, scaled-back aid-to-cities package, but without a modest portion Carter had sought that would have beefed up Housing and Urban Development Department grants.

Housing subsidies: The Senate cut HUD's authority to commit funds for future years, but the House increased it by almost as much. Neither action, however, will affect spending for fishal 1980.

Education: Carter asked for a reduction in part of the impact aid program for school districts adjoining federal installations. The House approved half of these cuts, while the Senate rejected them entirely.

House members also approved some $400 million in extra spending for grants involving higher education, aid to the handicapped and added money for the longstanding Head Start program. The Senate left Carter's budget intact.

Rural homeowner assistance: Carter proposed new aid for homebuyers in rural areas, but the Senate rejected the program and the House allowed only half the $1 billion the president sought in authority to commit funds for future years. The plan would take effect in fiscal 1981.

Revenue-sharing: The House flatly eliminated the portion of the federal revenue-sharing program earmarked for the states-about $2.3 billion. The Senate voted to continue the plan. A compromise is in the works.

Fiscal assistance: The House approval intact a Carter plan to continue a modest aid program for high-unemployment cities. But the Senate refused to budget for the plan, at a "savings" of $150 million.