Tvheadend

Under the Digital Video Recorders Profiles tab there is a setting in the Parameters section called "EPG Update Window" which lets you pick any of a number of times from a dropdown, however when you click on Help for that screen, nothing at all is mentioned about this setting, and I for one am mystified as to its purpose in this context.

I have filed a bug report asking that the help file be updated to explain this setting, but in the meantime does anyone know how it's used or what it's for?