RTP is a game’s long-run return; the house edge is the casino’s average share:...

https://varimail.com/articles/does-session-timing-matter-in-online-casinos/

RTP is a game’s long-run return; the house edge is the casino’s average share: 96% RTP means a 4% edge. Volatility affects how often and sharply results swing. Short-run results can differ widely from the average, so don’t expect a session to match it.