That should be more than good enough because I believe the usual purity for fuel is about 99.8% and even if that extra .3% impurity is water then no problems. I've added up to 3% water to fuel and didn't notice any difference in starting or running characteristics. But with 4% water all the oil fell to the bottom of the tank and it was impossible to start the engine (it seems they won't run on pure oil ).

JCINTEXAS has the right idea for mixing fuel because he's using a metric system where you can work out the volumes needed in your head, no calculators needed .