Come back when you are 25 and post your pics
I am not for one moment doubting you can have 20 inch guns at 25, but whether that would be at 15%BF is another question.
Some days back there was another chap who believed he exceeded natty potential and was around 12%BF. Turned out that pics looked like somebody with more like 16-17%BF and well below the predicted potential. If folks test their BF% carefully enough they will be surprised at how deluded they might have been.
It does not matter whether Mr Butt believes you have maxed out at 18. It does matter though that till now NOT ... A ... SINGLE ...bodybuilder
has surpassed those figures.
FYI, neither did this bear.
If you did surpass those predict potential by a significant amount, then you would be a genetic wunderkid superior to Parks, Grimek, Eder et. al. So, if you did, that would be a first of a kind. So, please post some snaps and let us celebrate the freak amongst our midst.