First off it has to start with the first pitch of the first attempt.
If it's going to be a ball and you swing and completely miss; the pitcher will continue to throw outside the zone until you either strike out or it ends up as a 3-1 count. Then they'll throw it close, if not, in the zone to see if you'll swing.
If you don't swing, making it a 3-2 count, the next pitch is going to be a ball about 75% of the time.
Now if the first pitch, of the first attempt, is thrown for a strike (taken) then the next one will be another strike about 75% of the time. Once you get to an 0-2 count they'll either throw it away out the zone or try to catch a corner/end of the strike zone.
Need to do some more 'practice' to see if this actually holds up and is consistent.