CALCULATING BOTTOM OF PIPE

Hello 

I have a problem with the BOP command. 

In a size, when I am using the command p1bop in command window, the elevation is not given correct, and it is different with Explicit coordinates. this problem is for every components.

I don't know why this happens. How the BOP is calculated in PDMS. 

I'd be thankful, if anyone could help me on this regard.

Thanks in advance