Trail order to avoid falling knife, didn't work

I read about this technique somewhere Yesterday i tried for the first time Trail order on MSFT with 5% I thought 5% is sufficient Then it went up from 398 to 403 something like that, and my orders got filled, wtf Isn't 5% of 400 equal to 20 ? I would expect it goes up 20 points up before it gets filled What kind of sorcellery is this And now of course i'm down