What’s happening is the theme is labelling the page automatically for you (the small grey title), and then within your policy yourself, you’ve started the policy with typing “Return Policy” as an H1/H2/H3 font size.
The easiest fix would be to go into your Refund Policy settings (admin > settings > policies), and then delete the title “Return Policy” from the top of the actual return policy (or else make it regular sized and left-aligned).