So I wanna use h2o2 for root health and oxygen

I want to use h2o2 for root health and extra oxygen to t he medium. But all I could get above 3% was 29% and not sure what the mix ratio is and can't find it. This says 3 ml per 4 liters. But a gallon is only slightly less than that 3.78L. I suppose going by that it should be the same yes?

So just use a lil less than 3ml in the mix

Thanks