Someone at Samsung accidentally flipped the switch on the Android 8.0 Oreo OTA update on that particular model in that particular country, updating the device to Samsung Experience 9.0 before even the Galaxy S8 saw the official update. Whoops.
There are a few possible explanations here, the most optimistic being that Samsung has the update ready to go for S7 Edge users and they’re just waiting for the Galaxy S8 rollout to finish before making it happen. It could also be a developer build or a beta build, in which case one lucky user is about to ride out some seriously unstable software until this gets figured out.
Either way, this should be a good sign to everyone else with an S7 model, as it means Samsung has at least already started work on the newer software for the slightly older flagship.