https://en.wikipedia.org/wiki/Rich_Text_Format#Code_example

From their example:

    $ echo "{\rtf1\ansi{\fonttbl\f0\fswiss Helvetica;}\f0\pard
    This is some {\b bold} text.\par
    }" |wc -c
    86
    
    $ echo "This is some bold text." |wc -c
    24

Also see cd34's comment.

If you're going to add information, that has to be a higher byte count.