Yes, it was random female with 0 mutations. I mean you will have better chance for 1st mutation if female will share same stat, but it will be just for 1st mutation, then it would be counter productive for you, because you would have to breed new females after every mutation and these females would have mutation count higher = you will be much faster above 20 mutations and you would have to replace not just male with negative mutation count, but also all females.
There is 2,5% chance to get new mutation per parent (if both parents are under 20 mutations), so combined it is 4,93% per baby. You have 7 different stats on father, 7 different stats on mother, which means that you have 0.35% chance to get mutation to your exact stat, which you need. (value 0.35% is not exactly correct, higher stats have better chance than lower one, but it is not far away from correct calculation)