Because you have different durations at different times, that adds a little more complexity. If you are OK with 15 seconds each time, it's simple:
Fallback OFF
OSC 000:00/000:15:/239:45 Then ON
If Time 20:01 To 07:59 Then OFF
This would use a repeating pattern of 15 seconds every 4 hours, but would skip the hours between 8:01pm - 7:59am.
But since you want some of them to be 15 seconds and some to be 10 seconds, you will need a couple virtual outputs to act as the timers, then control the physical mister output based on the virtual outputs:
[10_seconds] -- virtual output, turns on at 12pm, 4pm for 10 seconds each
OSC 000:00/000:10/239:50 Then ON
If Time 00:00 To 11:59 Then OFF
If Time 16:01 To 23:59 Then OFF
[15_Seconds] -- virtual output, turns on at 8am, 8pm for 15 seconds each
OSC 480:00/000:15:/239:45 Then ON
[Mister]
Fallback OFF
Set OFF
If Output 10_Seconds = ON Then ON
If Output 15_Seconds = ON Then ON
To get this set up, be sure to read my tutorial on Virtual Outputs:
https://www.reef2reef.com/ams/neptune-apex-programming-tutorials-part-5-virtual-outputs.703/
Also read my tutorial on Apex Timers for details on how OSC and If Time works:
https://www.reef2reef.com/ams/neptune-apex-programming-tutorials-part-2-timers.689/