Add your checks: 12.56 + 52.11 + 26.03 = 90.70
Subtract that from starting balance:
463.76 - 90.70 = 373.06
Add the deposits:
373.06 + 101.32 + 10.98 = 485.36
Your balance is correct.
Subtract your balance from the bank balance:
511.39 - 485.36 = 26.03
The difference is the amount of one of the checks you wrote, which means that check has not been cashed yet.
You did not do anything wrong.