Game concept · All Under Heaven
Mandala Ritual Tier
The game also links it as Ritual Tier.
From the game's encyclopedia
The Ritual Tier of a Mandala Ritual indicates just how much that destination would benefit from your admonition as well as the rewards for you, personally.
The game's text for patch 1.20.1.2. Words in blue are entries of the encyclopedia: hover one to read it, as in the game.
Mandala Ritual Tier is an entry of Crusader Kings III's in-game encyclopedia (All Under Heaven). The game explains it: "The Ritual Tier of a Mandala Ritual indicates just how much that destination would benefit from your admonition as well as the rewards for you, personally." It is part of Mandala Ritual. The game also links it as Ritual Tier. Patch 1.20.1.2, from game/common/game_concepts/tgp_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/tgp_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.