BTU ratings by companies vary also, depending on how long they test for in terms of whether they do 15 min testing and multiply that by 4 or 30 min testing and multiply it by 2 will change the BTU.
Also depending on the type of gas used in testing also will change BTU. Be careful of BTU ratings as they can be changed based on a lot of variables.
Please understand that Kovea has low BTU ratings because they test with just Butane and not Iso Butane canisters, this is done so that an accurate measurement will be made. Since all the different gas canisters on the market do not have an equal amount of Propane and Iso Butane mix, you can get different results.
There was mention of the SnowPeak Lite Max, its the same stove as this as Kovea manufactures the Lite Max.