i dont think thats the right info to figure out 'attempted credits'
and i think we would need more information as is to figure your shit out - you need to know how many credits (or credit points, possibly) each class was worth
example of how, at least i think how, my school does what you're taking about:
A = 4.0
Attempted Credits= 16.0 ( 4x4)
Attempted Credits= 12.0 (3x4)
then you at them all up - but im still not sure what the fuck you mean by attempted credits
i hope that helps