When you go to your hearing, UPS will typically attempt to negotiate with you.
For example, if you've documented -- with supporting witnesses -- $300 in penalties for management working, they may offer you $100. They'll persist that either management wasn't working, or that management had good reason to work, and they're merely trying to settle the issue - but they're willing to go to panel. They may even up their offer, but unless they've demonstrated clear, irrefutable reasons, you'll likely get your full payment. If you have a strong case, your manager may try to settle before any hearing (usually by adding time to your time card, over one or more pay periods).
If you do file, expect retaliation. It's also a good idea to get your steward to take witness statements (written or oral) since often the fear of retaliation leads witnesses to getting cold feet.
A couple years ago I was chased from the building at 3.5. Me and another employee would clock out and observe management work to complete the sort. My boss was adamant that supervisors had the ability to load air and pull add/cuts, and the labor manager & district manager seemingly agreed, insisting we were heading to panel. At the last minute, they agreed to cut us a check in the full amount. With a week, I received a certified letter from the district manager that notified me that if I did not vacate the building immediately after clocking out (I would be permitted to use the rest room near the entrance of the building, however) that UPS would consider me to be trespassing and I would be prosecuted to the full extent of the law. My BA laughed it off.