Great question. You would not believe how long and how often programers get this wrong.

There is even a list that is maintained of ROM chips that do weight conversions incorrectly becuase Dec(6,2) is used instead of Dec(13,5)

I even had to "show the math" on this exact thing a year ago when I had to explain why the weight conversion code used to change Pound to Kilos and vice versa was wrong in every appliation where I work.

Not understanding this math is why so many ships have a problem balancing thier loads.

Sometimes the cargo is weighed in pounds and the balast program uses Kilos.

Then someone uses a cheap hand calculator to convert the 100,000 tons in pounds to Kilos and the weghts off by at least 1,000 tons.