The Return to Player (RTP) Percentage Is Important. One important metric for assessing a slot machine's long-term profitability is its RTP percentage. The arami gameverage amount of money returned to players over time is represented by this number; for example, a slot machine with a 95% RTP should theoretically return $95 for every $100 wagered. Although it doesn't guarantee specific results, it does give information about which machines might have better long-term odds.