You seem to have forgotten to explain what this means with respect to the actual data. Obviously it doesn't affect the laying down of the varves. And if the source of the contaminating carbon is lower, it must have been there even longer. I can't see that this helps YECs!.
Anyway, if your point is correct - we should see a systematic bias towards the carbon age being older than the age calculated from the varve count - and older than the carbon dates measured for objects of the same age. Perhaps you would like to check that and reprot the results.