This number is calculated based on a function that considers hotspot density in the hotspot’s area. Rewards through the Proof-Of-Coverage are calculated based on hotspot activity, and then scaled by your hotspot’s transmit scale. If a witness activity would have yielded 0.1 HNT and your transmit scale is 0.5, the reward would instead be 0.05 HNT. Choosing locations with high transmit scales is essential to maximizing the efficiency of your hotspot miner. More details can be found in HIP 15 and HIP 17.
Transmit scale is a multiplier that is applied to rewards of any Hotspot that witnesses you. The scale also affects how many rewards you receive as a Challengee.
To counteract the effects of a lower transmit scale, it is recommended that Hotspots improve their antenna setup (outdoors, higher gain, higher elevation) so it can witness beacons of Hotspots further away, with potentially higher transmit scales. This ensures a low-scaled Hotspot can continue to earn at an optimal level.
More details on the Helium Blog.
How do I view my transmit scale?
You can also view transmit scaling in the overall Helium Network from the Explorer. When the map is loaded, click on the “Filter” button on the bottom right hand of the map: