http://en.wikipedia.org/wiki/Spaced_repetition 

This uses a system called spaced repetition.

I have changed the standard algorithm because it does not fit well with the knowledge, the first issue is the normal algorithm can space forever, so after x times getting the point right you would never be asked the information again, all the flash card apps that use spaced repetition have this issue. 

Most of the algorithms space too widely at the start, e.g. a lot of them like to do whole days, whereas I believe that revising in day one multiple times is useful. 

My changed force a limit on the spacing so that the timeout cannot go wider than 56 days. 

So here is how it works in the app, there is a base time out figure in settings it is in minutes and I believe the default is 240 so 4 hours, so all points start with this timeout, so in 4 hours time the point will timeout, if when you are asked the question in ANY of the revision processes, e.g. daily sheets/weekly sheets, bike lists, postcode revision, category revision the timeout is updated, get the point correct e.g. the green button and the timeout doubles so 4 hours goes to 8 etc, get it wrong or make the point sticky and the timeout gets set back to the default of 4 hours. 

So what happens is using timed out point you will be revising your less well known points more than your well known points, in maintenance is a stagger timeout function this just shifts the timeouts forward to make the process less daunting e.g. if you have 1000's of timed out points this will get the first one and time it out and get the next one and move the time out a minute forward and work its way through the whole set like that. 

atb 

alex