Why does /proc/<PID>/status contain four collumns of UID

[Electric_Pulse]

When you cat the status file of any process in the proc fs then under UID/GID you see 4 numbers in total, why?

 

[osprey]

The answer to your query is in the proc manpage:

Uid, Gid
Real, effective, saved set, and filesystem UIDs (GIDs).