RTP is the game’s theoretical average return over a very large number of plays;...

https://www.bookmarkingvictor.win/rtp-is-a-long-run-average-not-a-promise-for-one-session-96-rtp-means-a-4

RTP is the game’s theoretical average return over a very large number of plays; the house edge is the share it expects to keep. A 96% RTP means a 4% house edge, not a promise that you’ll get 96p back from every £1 you stake