"work area" VS "comp lengh" when making MOGRT

I set the work area lengh to 4sec, and comp lengh to 5sec for the mogrt.

I hope when people drag the file to their PR sequence, the default will be 4sec, but if the strench it out, it is up to 5sec as the maximum lengh.

is this the right setting and the right strategy? when i testing it in my PR file, it sill shows 5sec as default, so the work area won't affect the default lengh of the mogrt? should i try other way or add expression to set it up?