Understanding the Kitchen Log

Apologies in advance if this is a dumb question, but can someone explain how to understand this log?

Call DB Procedure 3 2 - Finished processing (I=0, O=0, R=5, W=5, U=0, E=0) - What does each letter mean? I am assuming I = input?, O= output? R = read? W = written? No Idea what U or E means. I'm assuming these numbers pertain to rows or records?

Thanks