From the game's encyclopedia
Level of Fame Impact increases or decreases the Modifiers gained from your current Level of Fame.
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.
Level of Fame Impact is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "Level of Fame Impact increases or decreases the Modifiers gained from your current Level of Fame." It is part of Level of Fame. Patch 1.20.1.2, from game/common/game_concepts/00_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
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Source: game/common/game_concepts/00_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.