Although I would argue it looks better, you don't have to use sequential numbers when defining ordered lists.

Taken from the Markdown Syntax Documentation (https://daringfireball.net/projects/markdown/syntax):

It’s important to note that the actual numbers you use to mark the list have no effect on the HTML output Markdown produces. The HTML Markdown produces from the above list is:

    <ol>
    <li>Bird</li>
    <li>McHale</li>
    <li>Parish</li>
    </ol>

If you instead wrote the list in Markdown like this:

    1.  Bird
    1.  McHale
    1.  Parish

...

you’d get the exact same HTML output. The point is, if you want to, you can use ordinal numbers in your ordered Markdown lists, so that the numbers in your source match the numbers in your published HTML. But if you want to be lazy, you don’t have to.