Trying to change font size but it doesn't happen

I am writing a long book and am trying to change the font size for a section heading. I highlight the text and change font size from 12 to 16 and it doesn't change. I get the following reveal codes: Font Size: 16 [12] pt. What does that mean? I can't change the size at all for some reason. It just stays at 12 pt no matter what size I choose. How do I get rid of this code. I can go to other parts of the document and it works fine.

BTW- I am trying to attach a document to this message and it doesn't support WordPerfect files?????? I tried saving as a Word .doc and that doesn't work either. I saved as .docx and it gave me a weird message. I am not sure it saved it correctly. I am did a screen shot of what I am talking about. The red cursor is next to the heading I want to change. you can see the Reveal Codes that I am talking about.