2 cups or 12.5 ounces

OK, so the recipe calls for 2 cups of flour and says parenthetically twelve and a half ounces and so I measure out the 2 cups (out of the ridiculous flour jar thing) and decided just for the fun of it, to weigh it. Less than ten ounces. This stuff freaks me out. 

Baking in general freaks me out and when the ingredients aren’t perfect doesn’t that screw everything up? That’s fully 20% of the flour missing. How can we bake like this??? When a recipe in Cook’s Illustrated, the gold standard of cooking (not to mention the gold standard of insanely-over-complex cooking) can be this imprecise how can we be expected to produce good (and I don’t even mean perfect) results?

I am going to start weighing ingredients.