As you can see above, it is an image of the monthly payout you will get based on the different Retirement Sum savings you at have age 55.
Retirement Account Savings at 55:
The FRS is 2x of BRS.
However, the monthly payout from FRS is not 2x of BRS (2x of $730 = $1460).
The same is for ERS, where the payout is not 3x of BRS (3x of $730 = $2190)
This is because the Effective Interest Rates (EIR) on each Retirement Sum is different.
EIR is the real interest rate return you get from your money.
a) OA earns 2.5%
b) SA, MA & RA earns 4%
c) First $60,000 of your CPF balance gets extra +1%
d) First $30,000 of your CPF balance gets extra +1% if you are age 55 & above