What RTP really means
RTP, or return to player, is the share of all money staked on a slot that is paid back to players over a very large number of spins. A slot with 96% RTP pays back €96 of every €100 wagered on average.
RTP says nothing about a single session. Over a few hundred spins your result can land far above or below it. Some casinos also run the same game at a lower RTP, so check the game info before you play.