That system seems wonky. Once WN was looking for a single volunteer MCO-MDW. I was traveling with my minor son (on a CP, too young to travel alone) and I offered. They said they'd take us, but only needed one seat, so only would give one voucher, which I accepted as it was pretty generous for 2-3 hours. But the computer popped out 2.

It was a few years ago, so maybe things have changed.