What does rtr atm his ret mean on a bank statement?

This is a refund for a historic ATM transaction. I got one of these from Natwest. According to the letter I received, I tried to take out £10 in 2006, didn't get the cash but my account was debited. So they have refunded it 6 years later, along with a 'goodwill payment' of £1.67. Part of their mission to become 'Britain's most helpful bank', apparently.