I don't understand how the penis can be made larger in any way...

An ex member of Thunder's place grew from below 6" to over 11" he is called DoubleLongDaddy - he has now started his own PE website.

LPSG member Motlissof grew from around 6" to over 10" so I'm not convinced that there are limits to growth.

All this happens over several years with consistent PE sessions!
Some gain more than others. Some, for whatever reason, do not gain at all. Since this subject is still a work in progress, it's difficult to say whether everyone can make such gains, or whether there's some sort of bell curve to potential gains.

(I'm certainly not discouraging anyone from trying!)
 
I gained 0.5" of length and 0.1" of girth in the first five months, then stopped due to an injury (clamped head squeeze - I do not recommend these), and only got back into PE a few weeks ago. I had lost a little length during my hiatus, but I have now regained all of that.

Definitely check out Thunder's or MoS, do the Newbie routine, go slowly, and be patient. I was pretty skeptical going into it, but once my dick got longer, I was convinced.