Yep zagraniczniak, that is exactly right.
Under this system, ideally you want to get your percentages up in the higher distances - but even then this will still lead to misleading interpretations. If your percentage putts in the 25-50 feet category starts to rise, your putting is improving - but equally your approaches are probably getting worse!
I have to say I find it a really annoying method of calculation - I want to know how accurate I am from each distance, but sadly there is no way of knowing!
I would suggest new stats, from 0-3.9 ft (the tap-ins) then 4-7.9 ft (the ones you need to be holing to score well), then 8-15 ft.
They'll never change it though I guess!
And agreed - I don't make allowance for the wind when putting.