I added a hint to the bottom of the description.

This is not meant to be an easy kata.

OK, good idea ;-)

example added:

• #Example

For n = 13, the result should be 17.

the numbers from 1 to n are:
1 2 3 4 5 6 7 8 9 10 11 12 13
we need 17 single digit labels:
1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3
each label cost $1, so the output should be 17.

Maybe add some example to description would be better.

Can you point out where is quite confusing? Thanks.