When you choose subscript, a predefined baseline shift value and type size is applied to the selected text.

1. Highlight the text you wish to change or if it is the whole content of the text box, select it and click the Subscript field from the text editing toolbar.

https://cdn.elev.io/file/uploads/Nx6j1ilgYkjKwwUzxKv9Jx2yWyIGUZG4VbEE9W71H30/BgMhwZepRHo-31G_tLsjfSg2KSbGA9LeYZKlcfYzM6Q/changing subscript.fw--xs.png

2. Save your page when you're done or continue editing.