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

https://station-wiki.win/index.php/Why_Do_Some_Sessions_End_Up_Way_Above_RTP_and_Others_Way_Below%3F

RTP is the game’s theoretical return over a very large number of plays; the house edge is the casino’s expected share. A 96% RTP means a 4% house edge, not that you’ll get 96p back for every £1 during one session