| Rating | Description |
| 0 | 95th percentile exposure < 1% of the DPEL |
| 1 | 95th percentile exposure 1% - 10% of the DPEL |
| 2 | 95th percentile exposure 10% - 50% of the DPEL |
| 3 | 95th percentile exposure 50% - 100% of the DPEL |
| 4 | 95th percentile exposure > 100% of the DPEL |