If you enable Delivery hours, emails will ONLY deliver within the set windows for the days selected in the settings menu. If you do not select certain days (for example Saturday or Sunday), emails will NOT deliver on those days and will be held until the next delivery window. If your intention is simply to not restrict delivery on certain days, while restricting it on others, make sure you select each day and choose the full time window for any days where you would prefer delivery throughout the day.