Fast response, but it didn't really make sense.
You need two ramshorns to reproduce, however, any snail you get from your friends tank will almost certainly already have fertilised eggs inside it - so it will multiply, assuming the goldfish doesnt eat it and/or the baby snails (I never managed to get snails in my goldfish tank).
The snails wont multiply rapidly unless you have a lot of organic waste lying around in the tank (uneaten food, dead/dieing plants, lots of fish poop). So if you dont want loads of the snails, just keep the tank clean. The snails are beneficial, they clean up whatever waste they find and convert it into more snails, they also eat algae.
But like I said, there's a good chance the goldfish will eat them anyway.