The policy won't run until the Mac checks in sometime after 12:30.

A couple of ways you could do it at exactly 12:30:
- Initiate it through Casper remote at exactly 12:30 (requires you to not be at lunch=bad plan)
- Make the policy available in Self Service at 12:30, users can kick it off
- Put a Launch Daemon on the Macs that will run at a specific time. You could either have it run the whole script or just call a custom trigger to run the policy from the JSS. Apple article on Scheduled Jobs: https://developer.apple.com/library/content/documentation/MacOSX/Conceptual/BPSystemStartup/Chapters/ScheduledJobs.html

Yes, like @Josh.Smith said, making a policy run at an exact time isn't easy. There's nothing built into Casper Suite/jamf Pro to make that happen, other than some of the methods he mentioned. None are great solutions, but its all you're going to be able to do really.

I have to make the Media visible at a certain time then hidden a few hours later. I can build this all in one plist correct? I can reference several different times and scripts within the one plist?