RTP describes the share a game is designed to return over time; the house edge...

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

RTP describes the share a game is designed to return over time; the house edge is the casino’s expected share. A 96% RTP means a 4% house edge. In a short session, results can swing sharply—past outcomes don’t guarantee what happens next.