Woot non-standard credit systems!
We have the 1-credit a class system, too. Labs are 0.5, taken completely separately from the lecture course. Registrar tells us to count each class as 4 credits, but that would mean I'm taking 24 credits this semester and that's outrageous...but it's definitely more work/time than 18 credits so I usually compromise and use 3.5-credit multiplier when people ask me how many "credits" I'm taking. To everyone else at school, I'm taking 6 credits this fall.