Here you can turn it on, set the amount allowed and also when it should reset...(weekly or bi-weekly). The reset is done automatically when the set duration has elapsed. Once you have it set up, exit out of Settings and reopen iWatchr.
iWatchr will automatically draw from that "extra score" whenever the daily allowed has been exceeded. Extra Exercise counts towards that overflow so if you go over your daily allowance but also exercised and in doing so brought your score back under the daily allowance, the extra overflow will not be drawn from. Once the next day starts, whatever was drawn from the extra overflow, if any, remains drawn from it. You cannot make up what was drawn from it another day. Exercise score can only replenish extra overflow and "help" you the day the exercise is done.
Notice now the days in your History log are color coded. Blue days are ones since the last reset and therefore those days count towards figuring into the extra overflow, if needed. Red days are days PRIOR to the last reset (basically weeks past) and therefore those days have no effect on the present week's overflow. Once the week (or bi-week) is up, iWatchr will automatically reset the score for you. You don't have to do anything. Once you received the message from iWatchr that "it has been a week" and the overflow is reset, you'll notice that the next time you launch the application, the days will have change to their respective color (red or blue). Once the feature is turned on, the week or bi-week starts from that day so if it's monday but you want your week to week tracking to start on a wednesday, simply turn the feature off for 2 days and then when wednesday comes, turn the feature back on and it will record from that day forth.