When do Mileage Upgrades Clear?

Just wondering as I've never done a mileage upgrade before. I'm flying IAH-FRA tomorrow and UA offered me 15K miles to upgrade to BF. Not a bad deal so I took it, but it still just says "upgrade requested" in my itinerary. The 15K miles were deducted, just wondering when the upgrade usually clears.

Checked online and there are 5 open seats in R so I figure my chances are good.

Thanks!