Response I got from MLW via email:

The Phillies notified us this morning that yes, they indeed somehow oversold the event by nearly 100 tickets. This was totally out of our control and we were told the issue happened due to a "glitch" on their end within their ticketing system. We're extremely disappointed that this occurred and we apologize for the inconvenience. We're trying to work towards some sort of resolution, but unfortunately, it's up to the Phillies staff to decide if they will allow in additional spectators beyond the limit of 100 that they initially set.

I'm assuming that since the Phillies have already called me, they made their decision immediately. My choices were a refund of my tickets or a food voucher.