[BRAVESaj25bd8]

I don't think there is much discrepency at all. jacobhurwitz explained it pretty well. The key is that t_exp and T-score are the number of seconds left. Therefore, the expected time can be negative because if you get a ball for example with less than 11 seconds remaining, it does not ever need to be put back on the field. Negative times actually do make sense here because they represent the "never" possibility for the time at which a ball must re-enter the field. Hope that helps.