RTP estimates the share of stakes a game returns over a very large number of...

https://tango-wiki.win/index.php/How_Do_I_Set_a_Session_Limit_Using_Expected_Loss_Math%3F

RTP estimates the share of stakes a game returns over a very large number of plays; it is not a promise about one session. A 96% RTP means a 4% house edge on average over time