When checked this will cause Gruss Betting Assistant to update its own database of all available markets. If you are running TBM 24/7 then this option should always be kept checked. The exact time of the refresh can be changed. In the screenshot below it is set for 1100 hours and 1600 hours.

As well as the scheduled refresh, TBM will try and refresh the markets 10 minutes before a scheduled off if no refresh has taken place in the last 60 minutes. No refresh will take place if the next scheduled off is less than 2 minutes away.