An important thing to understand before we move on: what we tend to call a "number" is actually comprised of several different aspects. It has a value, which is the count of things it represents; it has a symbol, which is made up of the numerals 0-9 which can be arranged in single- and multi-digit fashion; and it has a name. In day-to-day life, when we don't bother with anything other than the standard base-ten system, the three aspects seem essentially tied to each other. However, once we start considering other systems we find that the three aspects are actually separate. In base-ten the symbol "10" coincides with this many things: (o o o o o o o o o o), but in another system it wouldn't (and it may or may not be called "ten").
In light of those distinctions, I'm going to employ a certain formatting scheme in this post that will hopefully make it easier to compare base-ten with other systems. If I write out the name of a number with letters then I'm referring to the value. So by "ten" I mean a group of this many things: (o o o o o o o o o o). On the other hand, if I were to write "10" then I'm referring to the symbol formed by the digits themselves, and not a specific value or count of something. It gets a little less clear when we get to the name, since I'm already using the spelled-out word to indicate the value. But generally, if I put the word for the number in quotation marks I'm probably talking about it specifically as a name rather than as a representation of the value. A little confusing, but hopefully it'll make sense in context.
Now, if we were planning to switch to any system between base-one and base-nine we'd be all set for symbols: we'd have a few extra hanging around that we wouldn't need anymore. But since we're talking about switching to a system higher than base-ten, we're gonna need a couple more single-digit numerals to fill in the new gap before we reach "10" (which, remember, is twelve things in base-twelve). For now, we can just swipe a couple symbols from the Greek alphabet*. Doing so could give us a series of number symbols that looks like this:
1, 2, 3, 4, 5, 6, 7, 8, 9, γ, ψ,
10
Two values that were formerly represented by double-digit symbols, ten and eleven, are now represented by single-digit symbols, and the symbol "10" has been reassigned to represent a dozen of something.




