Hi Stelfy
I doubt it will be very much - not enough to miss the target due to a sight error (though any small POI errors at 10 will be magnified at 20 - most of my shots at 10 yds - double handed - will be in a 40mm ring ...but at 20 yards a lot more miss!) ... but as a precaution why not take test shots at 12, 15, 17 (or similar) just to make sure?
ATB
Jon