Changing

You can easily change the format of a numbered list by selecting (Format > Bullets and Numbering)(Numbering tab)
Any changes made to the bullet points will affect the whole paragraph so there is no need to select the whole paragraph.
The Numbered tab deals with single level numbered bullets.

Whatever numbered bullet format you used last, this becomes the default format. ?????
So the next time you use the Numbering button whatever bullet format you used last will be applied. ??????
Numbering - Applies the default numbering format to the selected paragraphs.