Before your first spin, nothing is certain
96.71% is the RTP of Big Bass Splash, which is the return across a very long run of bets, not a promise for one session. How often the bonus round comes is not known in advance. Your result in one session is random, whatever the RTP says, and a short session can end well below or above that figure.
96.50% to 96.52% is the RTP range of the other versions in the series. Which version Fairgo runs is shown only in the game rules, so check those rules before you spin. The version in play is what any RTP figure describes for your session.
x5,000 is the ceiling of Big Bass Splash, the highest multiple of the bet the game pays, and players reach it very rarely. At the A$10 example bet that ceiling is A$50,000. At the highest bet allowed here, A$250, it reaches A$1,250,000.