If you are using the oil injector you donĀ“t need to worry about the ratio. The tank feed the pump inside the side cover and the pump mixes it (injects it) with the gas before/as it gets to the spark to burn.
If you start to have engine trouble along the lines of bogging, plugs fouling. The first thing to look at is the oil injection system. You can always abandon it and go with mixing the gas and oil in the tank (were talking 2-stroke oil for mixing...I like Bel Ray ..is that still around) at 20 to 1 good luck