It means overrides from CHDK extra photo operations menu. When an override is active, CHDK will force it even if the camera wants to do something else. This is our way of doing many wonderful things such as exceeding Canon's artificial shutter speed limits. Most of the time you shouldn't have any overrides enabled unless you specifically want to.
In your camera, none are active, so nothing's wrong expect that you probably don't want OSD text on LCD when you don't have any overrides enabled. Did you delete your config file when upgrading? Note that allbest old-trunk and new juciphox based trunk (which I believe your 509 build is) are not completely cfg-file compatible (AFAIK).
Anyway, you may find a setting to get rid of the text in the OSD settings menu.
