RTP is a game’s long-run return: 96% RTP means a 4% house edge on average....

https://juliet-wiki.win/index.php/Why_Does_RTP_Feel_Fake_When_My_Session_Goes_Badly%3F

RTP is a game’s long-run return: 96% RTP means a 4% house edge on average. Volatility describes how uneven wins can be. Short sessions can differ sharply from RTP, so your balance may drop quickly or rise unexpectedly.