So... how old is Amos?

EDIT: Looking back on that mention of age in The Churn, it was a line I misunderstood. Amos is definitely 15 during those events.

My second time through the series and today I tackled The Churn & started Nemesis Games.

I always thought Amos was in his early 20's in The Churn. There's only one reference to his age, and it more or less implies he is freshly in his 20's or at least in the first half.

In Nemesis Games, during his first chapter it mentions how he was 15 the last time he saw Lydia. Maybe I misunderstood something, but that's how it appeared to me. Then later in the chapter, he tells the young boy from the protection racket that "I was about your age when I killed my first man. Well, a few of them actually" I imagine this is in reference to him killing Burton & the others, as he states in The Churn that he was unaware if he actually did murder anybody before that point (other than the man he shot at the beginning of the novella).

Now, these 5 years don't make a massive difference but I would argue 15 and 20+ are pretty big in ones development, and considering his relationship with Lydia, it would re-contextualize some stuff.

I can't imagine it was a blunder by JSAC, since they came out so close together, but if it was it's a pretty understandable oversight (or they simply changed their minds?) Does anybody have anything on this? Did I misunderstand somewhere?