So I got carried away with my soapbox on the virtues of canning. This pic is of the math I did to fix the other jam. I pulled out the electric scale, weighed a bowl, zeroed it out, then added jam. To that figure I divided by 16 to find out how many ounces I had. Then, I used the recipe equation to find out how much sugar to add. I used a pen and paper, and my brain.