Did you reach an answer to this question? If so, please elaborate... seems to be a similar question in below thread, but still I can't find a clear answer...
For me this could be a usefull tool, iso clipping, because having yield in 1 - 2 % of your model could be acceptable, or at least is a good indicator on the strength of the modell...
These are statistics on how much of the model is visible with current Iso Clipping settings. With careful interpretation, they can provide insight into "how much" of the model is above or below the Iso Clipping values specified.
Element: Number (count) of shown elements % (relative to total number of elements)
Geometric: Shown element volume % (relative to total volume of geometry)
Please see SOLIDWORKS Knowledge Base (KB) solution S-069593 for additional detail.
Jay is correct about how the Iso clipping numbers should work.
My problems wasn't resolved officially but when I studied my erroneous values further last year it showed out to be a bug having to do with sub assemblies which I forwarded to SolidWorks with simulation cases and all to show it. I don't use nor have access to SolidWorks as of lately but I'll try to write down what I remembered about the bug; I can't recall exactly what the conditions were to trigger it but I believe it appeared when you had parts arranged in different subassemblies and wanted to get the global or isolated Iso surface value of some assembly/part where in some cases these values are erroneous.
I showed this by creating a simple L-shaped part bonded with one other part of the same volume then applying a load so that the stress was concentrated in the L-corner. If you use a very course global mesh and resolve the mesh very locally in the corner you can easily spot if the Iso clipping numbers are reasonable correct with your eyes. Try building a few load cases where the parts are grouped in different ways (parts in assembly, parts in different subassemblies and so on) but identical setting and you could probably see the number are very off in some specific cases if SolidWorks hasn't resolved this yet or if my memory fails me.
Edit: It's a shame I didn't post the stuff here when I had all the details last year, if I get my hands on SolidWorks again I'll update this post. If you do try this and can pin down the conditions/symptoms more precisely please do and I can mark this as solved.