Tiers are determined via Adaptive Staking.
For more details about Adaptive Staking, please read the following blog post: https://blog.sapien.network/adaptive-staking-280b163f515d
The amount of SPN Rewards you can receive each week is determined by how much SPN you stake compared to how much SPN is being staked by the rest of the community members. The higher the tier you are in, the more SPN rewards you can receive.
Please send an email to [email protected] if you need additional help. A Sapien representative is waiting to assist you!