I have serious doubts about that number. The lowest ever BTC ATM fee I saw was 4% (same ATM now has 6.5% fee),

Procedure of selling BTC is simple as well: You choose the amount of BTC (in dollars, euros etc) you wanna sell ( usually its some round number like $100, $200, $500 etc) and when you chose the amount, QR code of the address where you have to send BTC appears on the screen of ATM. You take your mobile wallet, scan the code and send BTC. When you did that, ATM prints out a piece of paper on with QR code which you will scan on BTC ATM once transaction gets few confirmations (ATM I am usually using asks for 2 confirmations). If I am in a hurry I use higher fee to get it done asap, but usually I just go in a bar and have a beer while waiting for confirmation.