Yeah Eleven's been refereed to as the eleventh Doctor a few times, though that's explainable if he doesn't consider Hurt a "Doctor". Trickier is Ten's comment to Sarah Jane that he's regenerated half a dozen times since they last saw each other.
If 10 remembers The Five Doctors
, that's only 5 Regenerations if you don't
include Hurt. If it's since 4 he's referring to, he has regenerated at least
half a dozen times, so, it's still not an incorrect statement, since he didn't say "exactly" or "only"
Here in America, it's not uncommon to find people using Half a Dozen as an approximately 6 quantity
One Day I hope to be the Man my Cat thinks I am
Where are we going? And why are we in this Handbasket?