RTP is a long-run average; house edge is the casino’s expected share: 96% RTP =...

https://weekly-wiki.win/index.php/Why_Do_I_Lose_Fast_on_a_High_RTP_Slot%3F

RTP is a long-run average; house edge is the casino’s expected share: 96% RTP = 4% house edge. Volatility describes how uneven wins can be. In a short session, results can swing sharply, so you may lose more—or win more—than the averages suggest.