Can someone explain to me this guy numerous encounters with me?

So long story short, I was a classmate with this guy when we were an undergrad.we used to help each other in some classes, other than we are not really friends, we don't have any contact outside class.

At the beginning of the semester, I have saw him and waved to him, but he had ignored me ( yes he had noticed the waving but ignored it). Then after that I also ignored him whenever I saw him.

But today in the lab, I was talking with one of the TAs and when saw me he said the usual, like hey, blah blah. Then when the TA have asked us how we know each other, he had told her that we used to be classmates last semester and if it was not for my help he would not have passed those couple of classes?

So can someone explain to me what is the meaning of his behavior?

Thanks