1991 NBA Finals Game 2 Michael Jordan 15 or 14 ASTs, not 13

Now playing... Is it 15, 14 or 13 Asts? #Teaser 1991 NBA Finals Game 2 Michael Jordan. Big fan of the bullet pass. (Trying to remain unbiased, objectively observing) NBA credited 13. Based on my understanding of Today's NBA rules... I'd say 14. (What were the Ast rules in 1991 tho?)