Ah!
Leading Zeros. They are in front.
I have never used the type (.##) of formatting you show

\ (You can tell I am not an expert)
I use (but my other requirements are simpler)
Code:
{series_index:0>5.2f}
is what I use so I get: 12.34 (2 leading and 2 trailing the . )
BTW spaces in file names should be avoided ( - ) ->(-)
You are ending a title with a -
then making a folder?