Course Page Sorting Filter Issue

Hi, I have an issue with the sorting filter. I have provided the URL here. When u goes to this page, u click the “First Column”, it will come out the pop-up, then u choose “Category A”. After that, it will bring you to the page, then what I want is, when customer come to the course page, it will sort by sequence. What I mean is “A0, A1, A2…” like this. May I know which part can I modify in the course-archive-filter-bar.php?

The page I need help with: [log in to see the link]