I just extracted between 15 and 20 gals. of honey today. I bottled a couple  8oz. honeybears and 1- 12oz. honeybear [by filling to the brim]. I weighed the bottles with the lids empty and then my full bottles. Each honey bear contained over 8oz and over 12 oz. of honey after deducting the weight of the containers. I used a scale designed to weigh precious metals so it is very accurate.
I then repeated the test with the 12 oz. honey bear [which is supposed to be 1 cup by volume]. Once I removed enough honey back down to where the indented lid area started, the honey weighed exactly 12oz. [after deducting the honeybear weight], or so close there was no noticable difference. I then filled a honey bear with water above the indented area, and poured the water into a 1 cup measuring. The 12 oz. honeybear filled above the indented area ran over a 1 cup measuring cup. I then refilled the 12oz. honey bear with water just to where the indented area began and again poured into a 1 cup measuring cup. It ran over by just the smallest bit.
So, I would say based upon the above experiment [with my honey extracted today], that an 8oz. or 12oz. honeybear filed to the indented lid area, but not beyond, contains 8oz. or 12oz. of honey respectively. When the containers are filled above the indented cap area to the top of the container, they weigh slightly over 8oz. or 12oz. of honey respectively.