dBs are ratios--I am presuming that means for a signal applied to the right channel, you will get that signal on the left channel at 85 dB below the level of the right channel. Since 3dB=double, the level of the undesired signal on one channel would be 1/60,000,000 (give or take a bit) of the desired signal on the other channel. Pretty negligible in my book...
I think... but I could be totally wrong...
I think... but I could be totally wrong...