So - if the Ad Group has more than one ad, the system will calculate min CPC for all the keywords in the Ad Group, based on the performance of the best ad.
BTW, this is what I was getting at, in my earlier post, I said:
In other words, this is yet another reason to make sure that all of the keywords in an Ad Group are about the same thing as the ad: because how well the ad does is dependent on the 'success' of the match between keywords and ads.
I heard someone call this a virtuous cycle - which I like a lot.
That is virtuous, not vicious!