The 10 is your base. We're assuming he is setting his dials using base 10, 0 through 9. Base 16 would be 0 through 15, so you would replace the 10 with 16. Likewise, if you're counting using any other base, you would just replace the 10 with whatever your base is. If you have six digits possible, your base would be 6.
Now as for how he would actually write his cases out, that would be a lot more work for him, since he would want a calculator on hand unless he is really good with converting bases in his head. LOL Like, I can kind of convert base 10 over to base 8, base 16, or base
2... But it would take me awhile to convert base 10 over to base 6. LOL but yeah, writing out base 10 or base 16 is pretty straightforward, assuming he is familiar with writing in hexadecimal.
So let's assume he is using base 11. Then 2-3-4 would be 279. Now, if game maker is still as thorough as it seemed to have been back in last time I tested, he could just write out the formula for every case.
case (2*11+3)*11+4:
The compiler, from what I could tell, would calculate that out itself, not force it to be calculated at runtime.