I shop in 9500 Wil and am a good fish eater. I regularly buy fish at Migros or Coop.
Unfortunately, I have noticed that when I dab the fish dry at home and then weigh it, the weight is at least 10-15 grams less than it says on the label. In my opinion, this is not correct and I could imagine that the scales are also weighing the paper, which the store is not allowed to do. I would therefore ask you to report this to the store and change it accordingly.
At the Coop, the weight is always correct. Always the same gram - exactly.
Many thanks for reporting this to Wil.