Slowness doesn't work

I was playing normal mcbedrockedition, and messing with commands. Then, I wanted to do the affect "slowness", and did slowness 5, then 250, but 250 might have been a kind of slowness that might made your player not move, but when I did 5, I didnt move too, so I kind of thought this was a bug. So, I think this is a bug that made my player not move.