You've got it right, Davey, as long as you understand your own words "it means 10 is 8."
When you use different counting systems, the count is the same, but the numerals you use to represent them are not.
Binary just uses 0's and 1's for everything. When you see
1011
in binary, you know that is not the same thing as one thousand and eleven, which is what "1011" means in base ten, the system we're all used to (decimal). It actually represents eleven. (I think. My base calculator is a little glitchy after the last update).
The octal system on the page mentioned above is base 8. Something in between binary and decimal. It doesn't just use 0's and 1's. It goes up to 7 before it starts over again. "10", a nice round symbol no matter what base you use, equals 8 in octal. There are no numerals "8", or "9" in octal.
Dozenal, base 12, the main subject of this thread, needs two extra symbols, since decimal only gives us 0-9.
But again, the numbers don't change, nor do their interrelationships. Only the representations change.