Hi Mark, I would suggest you speak to your nurse tomorrow for clarification on this to be on the safe side.
The insulin units to carbohydrate in grams is usually written as 1:10 ( one unit insulin to ten grams of carb ) Or else the ten grams of carb are expressed as a carbohydrate " portion " each which contains 10 grams . Confusing, I know !
So if you have been told one and a half to one, it means that your ratio is one and a half units of insulin for each 10 grams of carbohydrate you will be eating at that meal.
The 2:2 IS confusing, as that means 2 units of insulin per 20 grams of carbohydrates, but that is the same as 1 Unit per 10 grams. It's an odd way of writing it, hence my advice that you check with your HCP.
You may find this online course on carb counting helpful:
http://www.bdec-e-learning.com
I hope that helps .
Signy