it's just octal, octodecimal would be something like base 18 smile

The numbers in base just represent the number of different digits you can have before needing double digits (ie 10)

binary: 0, 1, 10 -> 2
octal: 0, 1, 2, 3, 4, 5, 6, 7, 10 -> 8
decimal: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 -> 10
hexadecimal: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F, 10 -> 16 (0x10 hex means 16 in decimal)