Let's use an example so it's easier to understand. Using normal natural delivery for example:
CPF says maximum you can claim from CPF Maternity Package is $1200, which consists of:
1) $750 for normal natural delivery (Normal assisted, C-sect will be different amount)
2) $450 for pre-delivery expense
Let's say you stay 3 days 2 nights. According to CPF, you can claim room rate of $450 per night. Hence $450 x 2 = $900.
So you bring the gynae's bill to the hospital you are delivering. They will claim from Medisave:
$750 + $450 + $900 = $2100
And this $2100 is used to offset your hospital bill.
Hope this is clear enough