A preliminary internal report on the D.C. Summer Youth Employment Program indicates that an average of about 16,000 youngsters received city paychecks each pay period during the nine-week program, considerably fewer than the 20,000 that Mayor Marion Barry has claimed to have put to work.

However, Matthew F. Shannon, acting director of the city Department of Employment Services (DOES), labeled the report "incomplete and inaccurate." He also said city payroll forms show at least 18,598 persons received at least one paycheck during the program and that final figures expected in several weeks will show total participation close to 20,000.

High turnover during the summer may account for the difference between the average payroll in the staff report and the total participation figures provided by Shannon. "You never have 20,000 checks for 20,000 people on any payroll. It is a fluid payroll," he said.

The city's official plan for summer employment was to provide 19,825 jobs using city and federal funds. In addition, D.C. officials planned to refer about 1,200 more youngsters to jobs in private business or other goverment agencies. But the preliminary report suggests that weekly payrolls fell far short of the 19,825 goal.

The report, dated Aug. 28, said that as of Aug. 9, the final week of the program, 25,424 youth had registered and 20,547 had been referred to jobs. Of those, the report said, an average of 15,809 persons actually worked and received paychecks every two weeks, according to DOES payroll records.

The attrition rate, comparing those offered jobs to those who actually worked, was therefore 23 percent, according to the report, written by Alvoid Johnson Jr., who is responsible for coordinating services for youths in the program.

"This rate is somewhat premature, at this time," Johnson noted, because the city is still receiving late "time and attendance" sheets from many worksites. Those sheets, certifying that youngsters actually worked, must be received before paychecks are issued under DOES's summer program. However, a DOES source familiar with the operation said late sheets are coming in at a rate of only about 100 per week and will not substantially alter the final count.

Shannon said Johnson's data were wrong because he compiled the report hastily before taking a leave. Johnson could not be reached for comment. Shannon also said the staff report fails to include the estimated 1,200 jobs provided from sources outside the city's main summer payroll.

Ivanhoe Donaldson, Barry's campaign manager and former DOES director, discounted the preliminary report and said: "There is no question that the program met its goal. We had over 20,000 young people working."

The summer program, plagued in recent years by late and missing paychecks and frustrating administrative snafus, has been credited with substantial improvements this year, according to city officials and the regional office of the U.S. Labor Department's Employment and Training Administration, which funds about half the $15 million program for youngsters 14 to 21.

A source familiar with the summer operation said several thousand young people could have been placed in jobs if DOES moved more quickly to offer jobs to youngsters on its list. Several thousand jobs opened up during the summer because the original registrants either failed to show up, turned down the jobs, or stopped work after a week or two.

"We never employed 20,000 kids and they knew it from the first day," said that source, who asked not to be named, "Why they didn't get back and fill in for all the no-shows, that didn't make sense."

Shannon, disputed that assessment and said the job referrals filled virtually every job for which there was an available worker.

Shannon acknowledged that about 3,000 youngsters who registered were never offered jobs. He said many of them had specified that they wanted only particular types of jobs, which often were not open. Other youngsters, he said, were not available when DOES tried to refer them to jobsites.

Shannon said it is unfair to use the preliminary report to judge this year's program, which he said "has been regarded as absolutely successful. . . In the past, you'd hear about a little girl who signed up for a job as a botany assistant and ended up sweeping streets. This year, you hear parents say 'My young person had a positive experience. They applied for a job and got the job they wanted.' "