Wrong charges returned by Australian Post API?

I'm trying to provide users of my site with postage calculator and to do so need to pull out data from australian post API (http://drc.edeliver.com.au/ratecalc.asp), but what is returned dosen't look anything like what get at Australian post website calculator at http://auspost.com.au/apps/domestic-parcel.html

I've tried with different settings, countries etc. and nothing seems to work. Data is returned with no error but charge and number of days makes no sense. E.g.

http://drc.edeliver.com.au/ratecalc.asp?Pickup_Postcode=2216&Destination_Postcode=0800&Country=AU&Weight=600&Service_Type=STA开发者_Python百科NDARD&Length=300&Width=300&Height=200&Quantity=1

When same data calculated at AustPost page http://auspost.com.au/apps/domestic-parcel.html gives me much higher charge.

I would like to avoid going thru sourcecode of countless modules for various shopping carts and so if anyone could point out what am I missing here that would be very much appreciated. btw I'm using php with curl.

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Why do you believe the data doesn't make sense? Your API link says the charge would be 13.15, and the Postage Assessment Calculator does the same (settings: From 2216 to 0800, Weight >500g - 1kg, Dimensions 30,0cm x 30,0cm x 20,0cm, Regular Parcel)