Numbering issue

Your screenshot shows a p is selected rather than an li. I wonder if you have Autonumbering set up, rathar than lists.

I've never used it, but from a quick test, if you are, I think you need to click in every paragraph and check what number is configured for each paragraph. Delete the number for every paragraph where you don't want a custom number. 

Your image shows the item is a paragraph rather than a list item.

1. Create a new temporary topic.
2. Create a list from the toolbar and enter a couple of items.
3. Press Enter twice at the end so that the list is stopped.
4. Enter some text in the paragraph and press Enter again
5. Start a new list.
6. Can you restart the numbering in that list?

Yes, I pressed Enter when I changed the number in Properties to 3 did 

In the Authoring area you pressed Enter to start the new list item and entered some text. When you changed the number in Properties to 3 did you then press Enter there? 

Yes, I pressed Enter and typed some text.

Have you pressed Enter?

Have you entered any text in the list item?