RTP estimates long-run returns; the house edge is the casino’s average share....
https://www.logo-bookmarks.win/rtp-describes-long-run-returns-96-rtp-means-a-4-house-edge-not-a-promise
RTP estimates long-run returns; the house edge is the casino’s average share. At 96% RTP, the house edge is 4%. Volatility affects how swings feel. In a short session, results can differ sharply from those averages.