The interest rate is only 1.2%. You'll get additional RM5 if you maintain a balance of at least RM5000 and do no over the counter transactions.
The 2.4% is when you add 1.2% of RM5000 and RM5. So, at RM5000, you'll get 2.4%. At RM6000, you'll get 2.2%. The calculations are assuming you get RM5 rebate every month for a year.
Basically, you'll get the highest returns in % if you have just RM5000 in account. Any amount higher or lower, you'll get a lower return in %