Mitch Kupchack's future will be determined within the next 15 days. But no matter where that future leads, it will include and estimated $6.3 million.

Mitch just came in and signed the offer sheet. It will be in the Bullets' hands in the morning," said Larry Fleisher, Kupchak's agent, from his New York office late yesterday afternoon.

So now the countdown begins. Jerry Buss, owner of the Los Angeles Lakers, has offered Kupchak an estimated $9000,000 a year for seven years. The Bullets, in return, have several options in dealing with the 6-foot-11 Kupchak, a reserve center-forward his five years here. They can trade him or ignore the offer and let him join Magic Johnson and Kareem Abdul-Jabbar. The options must be exercised with 15 days, although a trade would not have to be consummated in that time.

"It wouldn't surprise me a great deal if the Bullets matched the offer, then tried to trade Mitch to another team, simply because there are so many possibilities," Buss said last night. "There are 24 teams out there besides us.

"I would be surprised if the Bullets matched the offer with the intention to keep Mitch. He just isn't worth that much money to them."

It is unlikely the Bullets feel they can afford Kupchak, who earned $122,000 (half of which was defeered) last year. It is believed that Kevin Porter's $250,000-a-year contract is the Bullets' highest now that Elvin Hayes ($450,000) and Wes Unseld ($400,000) are gone.