(EOS means no ill harm, just so you know
)
What he is trying to say :
Firstly - Adjusting any one of the X Y Z lengths will automatically adjust the others based on the scale ratio. This means the obj will ALWAYS be the same at any size in the program. No XYZ can be changed independently.
Height - Means the ACTUAL height of the helmet, may not mean that in the program you should enter it in the height tab > The objects co-ordinates may be wrong, which in turn means if you enter the Height into the Height box, you may actually be entering it into the Width or Depth boxes due to the OBJ's XYZ system.
Go to post : #1045 and use my tutorial on the distance checker tool, and keep upping the scale ratio until it is a little bigger than your head's dimensions.
^ people need to use that tool more, it fixes all of these 'My scale is SHIIPPPP' questions .