Hi,
Well, I don't see any problem.
You've configured the settings to have your listing in alphabetical order based on the product page and that's what the system does.
When you have product names like "rep en roer 1", "rep en roer 2", ..., "rep en roer 10", "rep en roer 11", etc, it's normal that you can an order like:
"rep en roer 1", "rep en roer 10", "rep en roer 11", "rep en roer 2", ...
since alphabetically speaking, "rep en roer 10", "rep en roer 11" are before "rep en roer 2"
If you want an alphabetically order on the product name while respecting the numbering, you would have to write:
"rep en roer 01", "rep en roer 02", ..., "rep en roer 10", "rep en roer 11", etc
So either that, or you configure the ordering yourself with the "order" column of the products listing in the backend, and you select "ordering" in the "ordering column" setting of your listing.