Auto Calculated SHAPE_Area & SHAPE_Length fields not working in AGOL/Collector

[LindsayRaabe]

It's good to see this feature has been added to ArcOnline (Calculate geometry in AGOL to find the area or length of a polygon or line).....BUT..... it is only good if it gives lengths and areas of meaning. How can I make my features calculate the Actual length and area?

Below is my test data created using Australia's GDA1994 MGA Zone 50 (1 Ha square with 100 metre sides and a 2nd rough square to closely match). 

The same 2 shapes published online with the Shape_Area and Shape_Length fields giving results that are clearly wrong. Instead of an Area of 10,000 m2 and Length of 400 m, I'm getting 14365.30 m2 and 479.42 m.