I'd have to double check, but judging by what you said Sort by filename suggests it uses asciibetical order, which is that annoying effect where files are sorted like:
Code:
1
10
2
20
A
B
C
a
b
c
So-called natural sorting will do that you actually expect, i.e., something like:
Code:
1
2
10
20
A
a
B
b
C
c
If you're wondering why it's even an option given that asciibetical is awful, I'm not sure. Maybe performance reasons if you have hundreds of files.