[Pierre]

12 generations 13 lives. Yes.

But what is being proposed in the earlier posts is that Tennant the tenth, but actually the 11 th doctor used up 2 regens.

Which means that Smith, the 12 incarnation actually came into being on the 12th regen.

We know that Capaldi is the 13th as it that made clear on the Saturday.

Which means to get to Capaldi, if we say that tennants second regen into himself was an actual regen, we need to magic a regen out of something.