Can someone expain kitchen scales?

I thought 4 oz = 1/2 cup but when I measured it it doesn’t. What is more accurate…measuring cups or scales?

It depends what you are measuring. Most home cooks measure everything in volume (teaspoons, tablespoons, cups, etc…) but professional Chefs only use volume for liquids. For accurate baking results it is best to weigh items such as flour because it is hygroscopic and its volume measure varies with the humidity.

4oz does indeed equal 1/2 cup in terms of volume. Only thin liquids such as water, vinegar, wine, etc will the measure be the same in volume and weight.