Those are apple snail (also sold as "mystery snail") eggs. From my experience, once they start breeding, they won't stop, so you're bound so see more over the next few months. Apple snails have lungs, so they breathe air, and lay their eggs just above the water line so they won't drown. Being in water might've ruined this batch. If you decide you want to breed the apple snails, just wait for the next clutch and let them be. They'll do their own thing. The humidity coming off the waterline should be enough to keep them going. After the thrill of my first clutch, I quickly realized I would be infested, and wound up chucking every egg clutch after that.

Once they decide they like your tank's conditions, they'll probably keep laying. They're not hermaphroditic, though, so if you can figure out their sexes, (which I could only ever do when they were going at it), you can separate the boys and girls to stop them breeding.