The only confusion is in the minds of people who were indoctrinated by overzealous physics teachers in high school. The legal definition of a pound *is* a mass.
What's confusing are the words "around five pounds (2.25 kg or so)". By the legal definition, 5 lb is 2.26796185 kg. Is that "2.25" just a round value (like "five" is)? Or is this an example of Klingons being sometimes inaccurate, but never approximate?
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De'vID