Halo Wars, Mr. Punctual achievement?

[Dakota]

In halo wars for the achievement Mr.Punctual.(Finish all missions under par time on heroic difficulty) I did it in co-op at first with my friend and then realized it was to hard and I did it by myself and i completed the game on legendary. Does it still count with both?

 

[dronkey15]

did u get it b4 the time was up???
if u did u prbably have it... if you dont
try it n easy or normal... theyre easiest