Sin'd bid was on 12:05, so a bid on the last 15 minutes because the end was 12:15.
So the new ending time has to be +15min from the bid on 12:05. So the new end of the auction is 12:20.
At least thats how I understand the auction rule 3.
Considering the bid on 12:20 (last minute) I am unsure just like Sin.