The burn rate is the ratio of the difference of the candle mass before and after burning and the total time overall burning periods. A burn period should be 4 hours, with a minimum of 1 hour between burn periods.
If a container candle weighs 540g before burning and weighs 350g after 40-hour burn, then the candle will have consumed 190g of wax over 40 hours. The hourly rate of consumption is therefore:
190g40h = 4.75g/h