[it was obvious but just in case]
Tonight is a make-up of the rained-out Nats-Braves match of Saturday 22nd April (our first home rain-out ever). If you're a season ticket or partial plan holder, or if you otherwise still have the ticket you would have used that evening...use that ticket (ticket to Game #5 if you're a full STH).
[Confirmed just now in call to Nats sales office]