@shampton82 -
So not a bug but user error, mis-understanding on my part of how "% of Total" works.
With y-parameter checked it appears to be: sum(y-parameter values, per factor)/sum(all y-parameter values);
With y-parameter un-checked its more like: N(values, per factor)/N(all values) - which is what I was looking for initially.
Thank you for the correction.
Ray