Feeds don't all weigh the same and not all coffee cans are the same size. So it's important for you to weight your feed yourself.
You can get a scale at Walmart for very little that will allow you to take the container you are going to be scooping with and put it on the scale and zero it out. This will mean that when you scoop feed and put it on the scale it will only be weighing the feed.
If you want someone else to double check you, you will need to give the name of the feed you are using and exactly what coffee can you are using (brand/size).
Licensed Veterinary Technician