A “cup” (unit of extent) is 8 fluid ounces.
If you’re looking to recognise what number of cups of xxxxx item to attain 8 oz. Of weight, we’d want to recognize the object so we can calculate that.
In case you’re looking to understand how many cups (as in the item used as a field for any other item) then we would want to recognise that glass’s quantity before we should decide how many it might take to reach eight fluid oz..