I worked with AppD support and they provided the below information which has worked for us:
In the example below we needed to EXCLUDE a time frame on a Saturday from Midnight to 4am
In order to accomplish this we had to actually create two health rules with two different schedules.
The first health rule will be for Saturday and the cron expression example is below:
Start Time = 0 0 4 ? * 7 *
End Time = 59 59 23 ? * 7 *
The second health rule will be for the remaining days Sunday-Friday and that example is below:
Start Time = 0 0 0 ? * 1-6 *
End Time = 59 59 23 ? * 1-6 *