Filename ordering

Hi,
the filename sorting that DOpus applies is quite strange to me:
000.txt
00a.txt
01a.txt
010.txt
Why 00a.txt is considered greater than 000.txt and 01a.txt lower than 010.txt?
I expected that the correct ordering would have been:
000.txt
00a.txt
010.txt
01a.txt
There will be an obvious reason, but I can't figure out which one it is.
Thanks for any help, best regards.

Numeric order filename sorting can be turned off. The logic is described here: https://www.gpsoft.com.au/help/opus12/index.html#!Documents/FolderOptions/Display1.htm

Hello Leo,
thank you for your very quick answer.
I read that article before writing my post.
The question is: where in DOpus v. 12.31 is the "Numeric order filename sorting" flag?
I converted the localization of DOpus into English, I opened "settings", then "preferences", then I searched for any preference with the word "numeric" in it and the result was an empty screen.
Best regards.

The page I linked to describes part of the Folder Options dialog:

https://www.gpsoft.com.au/help/opus12/index.html#!Documents/Folder_Options_Dialog.htm

Opened via Folder > Folder Options, near the top/middle of the main window.

To change the default Folder Options for all folders, see: Folder Formats: Quick Guide

Thank you very much indeed.
I've been able to find the right place to make the change.
Best regards.