You selected both, possibly. You can select more than one if you have the points in the pool to the top right of the console.

Having this same issue. Upon promotion, the soldier automatically gets ALL abilities for that rank unlocked. Anyone have a solution?

i'm also getting this issue

edit: hmm, it only did this for the first level-up. maybe i just forgot how this game works and by default first rank always gets both choices. regardless, not too big a deal, i was worried the soldiers were going to get every single ability, turning into invincible soldiers haha.