1. Create a new note, note the default point size being used (in my case it is 11)
2. Type some text, about 1/3 of a line's worth.
3. Change the font point size to something different, say 14. Continue typing but stay on the same line
At this point you have a line of text, part in size 11, part in size 14.
4. Highlight the whole line, and click to change the size to 11. It won't change. You must change the font size to something other than the currently used point sizes (in this example 11 and 14), then change it back to 11 to make the entire line point size 11.