If you want this subscript effect, select the letter "I" that needs to be subscript, then open the format menu, select the font tab in the font command, select "superscript (p)" or "subscript (b)" in the effect bar of this dialog box, and then click OK.
(shortcut key plus subscript: use Ctrl+? = key combination, press once to enter the subscript input state, and press again to return to the normal state. If you select the text first and then press these two shortcut keys, it will directly affect the selected text. )