If you're talking about the entry for STAR credit amount, that's for people who received a check from NY State. If you didn't receive a check and you just have your taxes reduced automatically with STAR, you don't need to enter an amount.
If you can't remember if you received a check or not, you can call NY State Dept of Taxation & Finance and they can look up the amounts they sent you and the dates they were sent. (Be prepared to be on hold for a while.)
