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

https://www.oscarbookmarks.win/rtp-describes-long-run-returns-96-rtp-means-a-4-house-edge-not-a-promise

RTP is a long-run average; the house edge is the casino’s expected share: 96% RTP = 4% house edge. Volatility describes how wins are spread out. In a short session, results can swing sharply, so your outcome may differ greatly from the average.