

If a person was ordering them, they would do it in numerical order. Despite these being numbers, the computer is still ordering in alphabetical order.
Doing it the way a person would requires the file manager to understand context, which requires a lot more logic for arguably little benefit.
I note that your season and episode start with 0 as well (S01E05), in order to ensure the alphabetical ordering works. Perhaps you should use 5.0 to solve this in the same way.
Just like the rest of my code.