only affects display.
Well... the negative numbers appearing as positive is only a display bug, the more salient point of negative "time remaining" being possible in the first place is at least a minor bug.
I guess they're only able to be expired when some scheduled check is run - same as the delay on re-offering funds with auto-renew.
Exactly as this guy said:
Shouldnt there be a check for that, like: if(expiration < 0) return swap;
Except it seems that the server is just a little tardy when it has quite so many swaps to run that check across.