Tick it if you post the listing only here. If the listing turns up on another site, the badge is removed for good.
When you post a listing only on realest.am, tick Only on realest.am in the form. Buyers see the badge and can search for such listings.
The badge is your word. If someone reports that the listing is also posted elsewhere and we confirm it, the badge is removed and can’t be added back. Listings imported from an agency’s feed can’t carry it, because feeds publish to other sites too.