Other ways to count slots in a narrative

You can count all the VARs appearing in a NAR and that is what I am doing. You just climb into the tree and return by adding sub counts. You do the same to count the "used" slots by checking the state of the underlying VARs and adding up the sub counts.

However it might make sense to consider weighting sub narratives equally, even when they contain different numbers of slots. EG if a two part narrative (A,B) has A=(X,Y,Z) and B=(U,V). Then the count of slots for (A,B) should be 1/2*(count for (X,Y,Z)) + 1/2*(count for(U,V)) = 3/2 + 2/2=2.5
The "used" would be weighted in the same way.
Update:  Or you could still have the total "amount" of slots equal to 5, but with 1/2 of the 5 devoted to A,B equally, and the other half to X,Y,Z equally. So the slots have individual weights as follows:
A and B each has weight 2.5/2  = 1.25
X, Y, and Z each has weight 2.5/3 = .8333...