Location of addon check_config output/logfile?

Hopefully a simple question. I am running the check_config addon prior to upgrading from 106.6 to 107.x. The output says ‘Successful config (partial)’ but I can’t see the full output (just the bit that is showing in the logfile window on the addon page). I assume the addon is writing to a logfile somewhere but I can’t see it. Any ideas where this addon writes to?
Also any suggestions whether partial success means I can upgrade and sort out issues after or does it mean it may break?