DB is not showing a schedule out that far, so I assume you are looking at the current schedule. Things could certainly change a year from now. However, looking at the current schedule, if you adjust the transfer time to a minimum of 10 minutes, you'll see that there is a 13 minute change there to Haarlem getting you there 11 minutes later than the original. If you put in a 15 minute minimum transfer time, then there is a 22 minute change there to Haarlem getting you there 16 minutes later than the original.
So you can see, trains to Haarlem out of Amsterdam Centraal are about every 5 to 10 minutes.