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

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

RTP is a long-run average; house edge is the casino’s expected share: 96% RTP = 4% house edge. Volatility describes how uneven results can be. In a short session, wins or losses can differ sharply from the average—RTP is no guarantee.