What 3 in USRBDX,USRBIN

Hi experts
I am confused with the what 3 option of selecting a unit. Does each USRBDX,USRBIN needs a separate unit number.bins Seen many experts using same bin numbers. Does all info about output stored in same file.
Please explain,
Any simple example would do as I am new to fluka.

Dear @sunil_cn,
Different types of scoring require different logical unit (i.e. you cannot have a USRBIN and a USRBDX on the same logical unit).
Instead, you can have more than one scoring on the same logical unit as long at they are of the same type (USRBIN with USRBIN, USRBDX with USRBDX, etc).
Then how many scoring to have on the same logical unit is matter of good practice, convenience, habit, and personal taste.

Thank you sir

Regards
sunil