Demand Sampling is a network feature used to collect real-world traffic data to evaluate how much carrier traffic a specific deployment is capable of offloading prior to being enabled for rewardable data.
When a hotspot is newly onboarded or its location is asserted to a new deployment, it automatically enters the Demand Sampling period for up to two weeks, which will enable the deployment to accept AT&T live traffic even if it has not yet been officially selected for rewardable offload.
AT&T Demand Sampling traffic that runs through your hotspot will not be rewardable. If your hotspot has previously already been selected for rewardable offload, or is actively selected for rewardable offload by another carrier such as T-Mobile, traffic from these carriers will be rewardable.