How to Precomp

I am a beginner here and need some help with pre-comps. Thanks in advance. 

"Linked Comp 02" is one shot that I pre-composed. 

The precomp  "Comp 1" duration is longer than my shot. Where I circled is the shot durtation of my first comp. 

When I trim the pre-comp to the shot duration, the clip disappears in "linked Comp 2."