https://ratings.fide.com/calculations.p ... 1&rating=0
The FIDE calculator states:
So what is happening here?K = 40 for a player new to the rating list until he has completed events with at least 30 games
K = 20 as long as a player's rating remains under 2400.
K = 10 once a player's published rating has reached 2400 and remains at that level subsequently, even if the rating drops below 2400.
K = 40 for all players until their 18th birthday, as long as their rating remains under 2300.
K = 20 for RAPID and BLITZ ratings all players.