Benjamin H. Alexander, president of the University of the District of Columbia, said yesterday that 867 UDC students--not 1,200, as he had reported earlier--will be suspended from the university because of poor grades.

Alexander said that an additional 3,047 students will be on academic probation at the start of the next semester on Jan. 17, nearly double the figure of 1,700 probationary students he gave earlier. There are about 14,000 students at UDC.

Alexander said that the numbers changed because his staff originally gave him the wrong figures. The university sent out a press release announcing the number of students suspended or on probation last week, before the registrar's office had completed its final review of the students' most recent grades, he said.

Alexander said that the numbers he released yesterday are final.

"A mistake has been made and this university is big enough to make it known," he said. "It was my understanding that all the homework had been done prior to the press release going out."

Under a university policy adopted in 1979, but not put into practice until last year, students are to be suspended if they do not achieve a 2.0 cumulative average after completing three semesters or 30 credit hours. Those students are barred from enrolling in courses at UDC for one semester.

Students who have been at the university for fewer than three semesters and fail to achieve a 2.0 average, the equivalent of a C, are placed on probation and are required to take a smaller course load than students in good standing.

When the first announcement was made public, some of Alexander's critics on the faculty accused him of publicizing the suspensions to bolster his image in the community as a no-nonsense educator bent on raising academic standards at the city's only publicly financed university.

"I think it was very unfortunate," UDC Faculty Senate president Wilmer Johnson said of Alexander's handling of the matter. "I don't think we needed this fanfare."

Johnson said he believed that enforcement of the suspension policy should be treated "as a routine matter, as it is at other universities."

"The president's retraction is indeed admirable and shows that he is a man of considerable integrity," said Kelsey A. Jones, a vice president of the Faculty Senate.

But Jones added that he believes the incident "strongly suggests that the university should not play out its academic scenario in the framework of the media."

Alexander said that he was not trying to gain publicity. "We are not happy to have 867 students suspended and some 3,000 on probation," he said.

University officials said that the 3,047 students on probation include those who were on probation when the school year began in September, plus students who have been placed in that status as a result of their work during this past semester.