I've asked this before but can't remember the answer! If I click 'numbering' every para gets a number. But if I hit 'back' then it settles down to what I actually want. What's happening, please?

See Formatting applied to one paragraph affects the entire document.

Also, consider not using those numbering buttons. They cause more problems than this. Instead, see How to create numbered headings or outline numbering in Ribbon Versions of Word by Shauna Kelly

Thanks Charles. I've made a note of it this time!