The preset loads two copies of the frequency program for you. So the 2 hour frequency program being repeated twice, will account for your 4 hours.
If you examine the frequencies, you'll see that it starts at 364.56 Hz and ends on 21822.15 Hz and then repeats the same pattern once more, finally ending on 0 Hz to issue a beep.
Unlike the Terrain Single Steps version where you have more control over all the settings, the BY version is setup to be as one click as possible.
Once you run the BY preset once in contact mode, you have met the requirements for both applications for the day.
For more details, please check the link: