I'd forget about the conversion stuff and just start from scratch like I did when I made them. I would remove the drain plug on the carb and let the fuel drain(in a gascan) till it quits coming out. That will place your tank in the empty position. There will still be some gas in the tank, but not high enough to enter the sediment bowl. Use your measuring container of choice and add one liter(or whichever measurement is for your area) and add one container at a time, removing the stick quickly and marking with a pencil, then continue this process one container at a time and marking the stick till your tank is full.
The main reason for the sticks is just for a quick visual check for gas. If it's barely visible on the stick----time to add, if there's a couple inches------good for several hours.
Rick--retired KubKraft employee