The confluence editor removes legitimate HTML attributes to start the numbered list entries at a particular start number.

For example:

• Demonstrated here: https://www.w3schools.com/tags/tryit.asp?filename=tryhtml_ol_start

  <ol start="8">
    <li>Coffee</li>
    <li>Tea</li>
    <li>Milk</li>
  </ol>

Renders a list numbered from 8. This is correct HTML entered in Confluence with the Confluence Source Editor

  8.  Coffee
  9.  Tea
10.  Milk

 After pressing [*Apply*] in the editor the page editor display and the preview display show the list beginning with one. Whe n

This is offered as the only solution for this problem in the Q&A section:

• How to continue a numbered list back in 2013, Five years ago.

Removal of this ability from HTML appears to be a REGRESSION error in the editor.