Using the button "Release Checked + Delete Others" does three things:
Messages are automatically released to the address or addresses that are shown after "Legitmate messages are sent to." If you want to change where messages are sent, do so before clicking the "Release Checked + Delete Others" button.
If you only want to release a message or mark a sender trusted, select the messages you want to release, then click on the button "Released Checked Only". You can still search and scroll through pages, if you prefer. Releasing and deleting messages as you go, though, makes sure that you're never re-reviewing messages you've already seen.