The IG has a value itself, however it's true that it's better rapported to the carbohydrates consumption. (And not just the sugar consumption) : the value of glycemic load (instead of glycemic index) do that.
To calculate the glycemic load value, the formula is pretty simple : GL = GI * (quantity of carbohydrates / total quantity)
In the case of Queal the GL for one meal is close to 30 ( = 70 * 78,7/178). That's too high, just like the GI.
For exemple, a portion of Watermelon is approximatly 150g witch correspond to 10g carbohydrates so the GL is 5 ( = 75* 10/150 ). This value seems incredible, but it's just that the watermelon contain propotionaly less carbohydrates than the regular Queal. As a consequence, the watermelon less increase the blood glucose level.
I don't have so much nutrition knowledge too, so tell me if i'm wrong.
(Sorry for my bad english, I'm french,I hope you will understand me !)
EDIT : The link given by @Floris_Queal includes Glycemic load for each food. And to respond to him : Queal is supposed to be eat alone, it's not the case with the other food just like Pasta eating with some other food (that probably reduce the GL depends of course of what you'll eat with)