what an ignorant person, probably trying to convince you to take more product anyway.
This is when I refuse to take more, even if it's 5g! Because it annoys me. There was one time when I asked for 150g of ham and the person serving me got 290g sliced and asked me if it's ok. That is almost double of what I asked and they still think it's ok.
Again, common sense. If you don't know how much to put in the box or how much to slice, you take one slice, place it on the scale and see how much it weights. Then calculate how many slices you need in total, even if you need to use a calculator. It is that simple.