Hello,
I am using the volume cover command to crop the chain from the protein map. Here is what I did:
> open 12554 from emdb                                  
> open 7ns0                                                     
> volume cover #1 atomBox #2/A1 pad 1.0
Suppose I want to add extra 17 voxels on each size of the chain, what value of pad should I add? Also, could you tell me the unit of pad in this command? 
Thank you very much.

Best regards,
Thu