Flour can be somewhat problematic to measure. Oh, it's easy if you have a good kitchen scale – I don't, yet – but if you measure with scoops there can be a huge variation in quantity.
If you just take a cup measure and take a firm scoop out of the bag of flour, you'll get somewhere around 5 ounces of flour, but it's quite inconsistent.
My technique is, I fluff the flour with a fork before each scoop, scoop, then level the top with one swipe of a butterknife. This gives about 4 ounces per scoop, and is somewhat consistent, though still not as good as weighing.
A scale! A scale! My kingdom for a scale!