Per my calculations with the given dimensions in your post, I get 1740 gms of weld metal per 1 meter of weld. I assumed 1 meter reinforcement (cap height) above the plate. This is 662 gms (1.4 lbs) more than your actual shop floor result which is about 3 or 4 rods maybe. I'm not sure how much one rod weighs.
I have attached a PDF of my calculations. I also compared it to FCAW just so you could see a cost comparison.
Hope this helps.
Mark Mruczek
Mruczek Welding Engineering
http://www.mruczekweldingengineering.citymax.com/home.html