Anub'arak kills, in 10-Man Trial of the Grand Crusader, seems to be taking into account previous Anub'arak kills inside 10-Man Trial of the Crusader.
There's probably never going to be a way to resolve this, based on Blizzard's inability in the past to go back and fix stats, so for now a successful kill of Anub'arak in 10-Man Trial of the Grand Crusader will be checked via achievements.