Men please tell me why a man would say this and is there a meaning to it?

Your talking to a woman that you have dated recently (mutual split) and you ask if your out of her system and she says yes (you weren't to happy about it but accepted it). Then a week or so down the line you speak to her and you make a reference about you being out of her system ( in a joking way) and she say "well actually your not" . She says that she thought you were and but your not. She says she was just so angry (didnt say it to hurt you)with the situation and thought she was over you. Now she knows she is not.

Here is my question; Why would he say well im gonna go with the first response ( yes your out of my system). I asked why would he go with that. I ask why and he kinda blew it off.

Guy if tha were you why would you say that?