Most likely it is still a 10 digit word with any other letter being a nonexistent filler letter & some repeater letters. Let's use the word blackhorse. Blackhorse 1234567890 we will use x or z as a repeater number Coin cost wbxkgz = $1155 W doesn't count, B is 1 ,x repeats the number before (1) , k is 5 , g doesn't count , & z repeats the last number before (5) . He's most likely just adding letters that mean nothing and reading through them. Or .....he's just super smart, keeping some sort of convoluted code or ....his code actually means nothings & he just uses his grey sheets anyway.