devtrackers.gg
I cleared and entire fort in Colcestre by assassination and it only counted for 19 assassinations. So then I decided to check. I assassinated someone, didn't count, it took 3 assassinations to count for 1, so the weekly challenge is bugged and we're working our butts off and not getting the results we thought we would get.
I suggested that Ubisoft fix this asap. It's worse than it ever was before.