A half-million-dollar funding increase requested by National Endowment for the Humanities staff for museum project grants will barely keep up with inflation, grumbled one member of the Endowment's advisory council yesterday.

"That's usually called modest growth," said Richard Lyman, Stanford University president and head of the public programs committee of the National Council on the Humanities. "What it means is you're going to take a modest punch in the jaw."

The museum grant was only one of the proposed budgets for fiscal 1981 considered yesterday. Budgets for public programs in library and media (film, TV and radio programs for national or regional broadcast) were routinely and briefly enumerated to the committee yesterday.

The public program committee -- which only studies a portion of the myriad grants the Humanities Endowment funds -- will report to the full National Council on the Humanities today during their closed session. The Council, meeting here through tomorrow, will also consider, in the closed session, the more debatable Endowment grant applications.

Although the Endowment has yet to learn whether it will receive its full requested $150.1 million for fiscal year 1980 -- which begins in October -- their application for funds for fiscal 1981 must be submitted next month.

Endowment staff said they would like the funds for museum programs to increase from $8.5 million to $9 million. The proposed request for library programs asks an increase from $3.7 million in 1980 to $4.4 in 1981 -- and for media programs for $9.1 million to $10.5 million.

Humanities Endowment chairman Joseph Duffey has told the House Appropriations Committee that he is in favor of controlled growth until he has the staff to handle more finances, according to one Endowment spokesperson.