Relative Seniority:
747 CA 17% of (11,700)
747 FO 73%

777 CA 14%
777 FO 65%

I think showing how many years on property the bottom pilot in a category has accrued illustrates just how senior these airplanes are. Most of us understand that it's a snapshot and that as attrition, transitions, displacements, growth and recruitment occur the picture will be ever changing. For someone outside, showing relative seniority (I think) doesn't convey as much. To each their own.