This is the formula used to calculate how much centrelink pays:

Hourly rate (3.68)x elligable hours (so 36 hours if 3-12hour days) x your ccb% x loading - which differs depending on hour many hours you use. Under 35 hours is 110% loading, 104% for upto 48 hours I think it is and 100% for hours over that.

EG If you use 2 days and receive 54%ccb it would be -
3.68 x 24 x 54 x 110 = 52.46.
You then deduct this from your centres full daily fee for 2 days - so if it we $70 you would have to pay - $87.54 for the week.

Hope that makes sense!

So 3.68