When I want to number something 5, 4, 3, 2, 1 in descending order, it will show up as being as 1, 2, 3, 4, 5.
Yeah, unfortunately that's how the "Markdown" (the formatting) works. It just creates a standard "ordered list" in HTML which always starts from 1.
You can get round this by adding a backslash \ before the dot:
5\. Number 5 4\. etc