Ok, he only finds out that this runt is 20 at the very end, so... pdf-file coded for sure.

Reading comprehension. He finds out his age as soon as he meets him. The second chapter is several months earlier than the first chapter, it's a flashback of when they first met

There's other reasons this is PDF codes but it isn't the age reveal

The reader only learns he is an adult after all the smut
This is concerning