RTP estimates a game’s long-run return: 96% RTP means a 4% house edge....

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

RTP estimates a game’s long-run return: 96% RTP means a 4% house edge. Volatility affects how often results swing up or down. In a short session, outcomes can differ sharply from the average, so a game’s RTP doesn’t predict what you’ll get back.