Contribution tree question

[schivlg]

I'm not clear what the values and percents in the contribution tree represent. Are they the sum of all processes upstream, the direct impacts from a process, or something else? Part of what is confusing me is how the contribution of something in the 4th level of the tree can be larger than the element it is direct under. In the image below I have circled three examples where Petroleum refining has larger Ecotox impacts than the fuel use it is under. Additionally, the electricity from coal in the 4th level has 92.92% contribution while the entire grid mix it is under only contributes 2.73%.

openLCA contribution tree.JPG (89.38 KiB) Viewed 5976 times

Running 1.3.0 RC 32bit on Windows XP.