Both Norrbys are correct. The way parcel/farm ownership developed historically on Gotland means it is very common for several nearby, today separate, dwellings to have the same name. On Lantmäteriets own (non-free) more detailed maps both are named, as well as in historical sources.
- https://minkarta.lantmateriet.se/plats/3006/v1.0/?e=720647&n=6423458&z=12
- https://historiskakartor.lantmateriet.se/hk/viewer/internal/J133-7J4e78/52414b5f4a3133332d374a34653738/rak2/RAK/Hall,%207J4e78/Ekonomiska%20kartan