5006 - GCN and PDC

I have recently bought a 5006 and find the manual of little help as far as setting up the Guide Channel Number is concerned. I found one reference to this in ‘search’ but it didn’t really explain how to do it. Also, when I activate PDC by clicking the edit button, although the red flag appears on the timer line, when I click ‘exit’ the flag disappears and, on replay, the recording doesn’t seem to have been controlled properly (recordings start/finish before/after they should). Any help would be appreciated. Thanks, Richard