You adjust the effective range of a beacon by modifying its signal strength. Depending on the physical parameters of the walls, the signal might or might not penetrate them. For Proximity beacons, the effective range can be anywhere between 100m and 10cm, so you’ll have to experiment with different settings and see if you’re able to match the dimensions of the room. Be aware, however, that due to the nature of radio waves, it’s impossible to have a 100% stable & precise system.