After Effects layer overlapping

Hi,

I cut my layer (at end) by using Alt + ] , But I keep seeing there is  'White shadow overlapping area'  ( in picture I marked that area in a red box).  (b)

also my layer keeps some area which should not be there.(a)

Why this translucent white area is being produced? I dnt want them. I want my laeyrs to be arranged exactly where I cut them.

What can I do to get rid of this?