RE: big mistake what to do
I agree with BC - 4350 is a slower burning powder than 4064 and the small amount of 4350 that you inadvertantly mixed with 4064 should be no hazard. I would, as BC suggest, mix the container well so this minimal amount is dispersed thoughout the can.
Reloading is serious business and major accidents can happen if you are not paying attention to every detail. Absolutely no distractions. Consider yourself lucky this time.