If there's a charge in your account that you don't recognize, it might be one of the following:

Usage fee 

It's possible that while riding, you went beyond the time that's included in your pass type. We have these time limits in order to keep the bikes in circulation and available for other riders. If your ride exceeds the covered time limit of your ride pass type, you'll be charged extra time fees.

The first 30 minutes of each ride are included for Single Rides and Day Passes, the first 60 minutes of each ride are included for 30-day members and Annual Members, and the first 3 hours are included in the Day Pass. Divvy for Everyone members have a ride time of up to 45 minutes.

Lost bike charge 

If you have kept a bike out for more than 24 consecutive hours, it is considered lost or stolen and there is a fee of $250 (plus tax). This can also happen if you did not dock your bike properly, so your ride stayed open, and someone else took the bike and has not returned it.