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

https://www.quantifiedstrategies.com/rtp-variance-and-expected-value-applying-a-quantitative-framework-to-online-casino-gaming/

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