purchased a quarq cinqo fsa-light and was able to sync it up to my garmin 800. I was able to sync and the avg wattage after a ride seems correct, but while riding, i noticed the realtime wattage numbers jump up and down sporadically and is not stable.

What is the +/- difference in wattage should i see when I'm pedaling at a perceived constant pressure and rotation?

I pretty much recalibrate the quarq the 4 times I've ridden it and the recalibration process numbers are within satisfactory range.