They've charged you a max fare for entry and exit at the same station, give it 48 hours to see if they auto refund you, If you don't get the refund you'll either need to register the card online at tfl - this will bring up your recent journey historys (worth doing if you think you'll use the card regularly or on future trips) and you can adjust the non- journey yourself by selecting the option from a drop down menu, or you can call 03432221234 and get cs to refund you.
How to get a refund if you have been charged for touching in and out at the same station.
tfl.gov.uk