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

https://riversinspiringcolumn.urbanvellum.com/posts/how-do-i-avoid-getting-tilted-after-a-long-losing-streak

RTP is a long-run average; the house edge is the casino’s mathematical share: 96% RTP = 4% house edge. Volatility affects how wins and losses arrive. In a short session, results can differ sharply from the average—there’s no guaranteed return.