It depends on repeating characters. If you can't repeat ANY of the characters, then there aren't 10 characters available for the 6th place, because one of them would have been used in the 1st place. The same problem exists for the 2nd through 5th places. Each time a character is used, the number of available characters for the next characters has been reduced by one. I think I had that laid out in the earlier post.

If you can duplicate characters, then your calculation is correct.