Nickel-and-Diming Riders? Part 3

From Anonymous:

I'm enrolled in Metro's "Threshold Autoload" where it automatically adds value to my SmarTrip card.

I finally looked at my usage report and discovered that if it reloads when I exit New Carrolton, but before I leave the parking lot, I get charged $8.25 for parking instead of $4.50!

Part 1
Part 2