Thespinningone: When I left the market today, I wanted fish. I had 200 rubles in my wallet. The seller said that he would not cut the fish anymore today, but there was a small piece on the shelf — and she offered me to hang it. It turned out to be 540 grams (I warned her in advance that I did not have enough money) - for 240 rubles. She says, OK, take a piece, bring the other 40 tomorrow.
I came home, started weighing this fish (to accurately calculate the proportions for the recipe) - it turned out to be 470 grams (the fish was not frozen, so it could not lose weight).
On the one hand, the importance is not so big. On the other hand, it’s still very unpleasant: I was hanged, and I still have to.
Take 40 rubles or go fighting?

gallon: 240 rubles / 540 g = 444.44(4) p / kg.
444.44 p/kg * 0.47 kg = 208.88(8) p.
So give 8 rubles 89 kopecks and ring.