Inside the app is a schedule this is customisable by you or you can create new schedules, simply put the schedule moves on with every good call of a run and when you make a mistake it starts the schedule again, what this does is over time moves all the runs you get right all of the time to a wide schedule and the runs you keep on getting wrong will be presented much more frequently, this is what timed out runs is all about, this can be done by every run, per book, per list etc.