Registry

I have noticed something puzzling when looking at people's registries online.

It says quantity purchased with a number... but quantity requested: 0.

Is it an error? Was it really requested but the system has it wrong? Or did someone go through the trouble of getting the registry scanned so the gift reports on the registry, even though it was never on the couples' registry? If it's the last one... why buy something the couple didn't put on the registry?

(This is not about us. Just wondering since I keep seeing this...)