If there's a charge in your account that you don't recognize, it might be one of the following:
Extra time fees
Single Rides, Day passes, and 3-Day passes incur an additional $2 for the first 30 minutes beyond the included ride time. After this, $4 are charged for the subsequent 30 minutes. Each additional 30 minutes will cost $8.
Annual and 30-Day members riders cost an additional $1.50 after the covered time period. If you ride lasts for 30 minutes beyond this, an additional $3 will be charged. After this, an extra $6 will be added to your total for every additional 30 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 $1,200 (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.