In the episode, he says he has been given "A whole new regeneration cycle." A regeneration cycle consists of 12 regenerations, as reaffirmed in the episode. He used 1 regeneration of the new cycle to become the Twelfth Doctor, so he should have 11 remaining.
Please note, however, that all our information about the number of regenerations in a cycle relates to the first cycle & we've never before encountered a Time Lord who had been given a second cycle. We cannot therefore know for certain that the number in the second cycle is the same as the number in the first cycle. In "Kill the Moon", the Doctor says, "In fact, I'm not entirely sure that I won't keep on regenerating for ever." Rassilon, in "Hell Bent", also doesn't seem sure there's now any limit on the Doctor's possible regenerations.