| Kind | Value | annotation | ||
| enumeration | 1_very shallow | |||
| enumeration | 2_very shallow to shallow | |||
| enumeration | 3_shallow | |||
| enumeration | 4_shallow to medium | |||
| enumeration | 5_medium | |||
| enumeration | 6_medium to deep | |||
| enumeration | 7_deep | |||
| enumeration | 8_deep to very deep | |||
| enumeration | 9_very deep |