I'm not convinced that the units conversion is right. The example of 2 Cups of greek yoghurt being 391.32 g. 1 US cup is 240 ml (or 236.5 ml depending on which type of cup you are using). The density of greek yoghurt is somewhere between 0.96 g/ml and 1.04 g/ml (depending on which website you trust the most). This leads me to calculate that 2 cups greek yoghurt weighs between 454 g and 499 g). The 391 g value is way off.

Thanks for pointing it out. I'll look into it and fix it by tomorrow.