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

https://www.pure-bookmark.win/rtp-is-a-long-run-average-not-a-session-promise-96-rtp-means-a-4-house-edge

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 are spaced out. In a short session, results can swing sharply, so outcomes may differ widely from the average.