Hi,
I'm sure you've figured it out by now but the // operator returns the "reminder". When you // by 10 this happens to be what would be on the right hand side of the decimal point but when // by 8 it's not.

(636/8=79.5)
636 / 8 = 79 and 636 // 8 = 4 because 79*8+4=636

(636 / 10 = 63.6)
636 / 10 = 63 and 636 // 10 = 6 because 63*10+6=636