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For one, percent and weight are not interchangeable units. I can't imagine why a thing is being labelled with a "kg" unit when it's supposed to be a percentage. It doesn't make any sense. It isn't the sort of problem that should exist.
For two, I can't imagine why someone has a thing in a (shopping?) cart that is measured in percentages.
Sweeping this problem under the rug is not the answer. You need to deal with the fact that WP or whatever is attaching incorrect units to the items. Because there's a really, really good chance that the wrong units are a symptom of a larger problem.