Low salinity acclimation

So I just brought two maroon clowns home from my lfs. I checked their salinity....1.009!!!! I'm running 1.026. I've added about two cups of water to 3/4 of a gallon of lfs water. I'm at 1.015 now. I've switched to drip acclimating now. Fish seem fine, how long is too long drip acclimating. Should I be too concerned.