The training program consists of six weeks (eight weeks if you can’t do at least 3 pull-ups in the initial test). Every week has three work-outs. You should rest for one day after each training day. For example you can decide to work out on Mondays, Wednesdays and Fridays.
If you fail to do enough pull-ups for the current work-out, step back one day. This doesn’t mean anything. Six weeks is short time for a training program. Take your time and don’t give up! You will be able to do 20 pull-ups sooner than you may think.