因為兼職的緣故15+2=17
That's where you're stuck.
It's not 15+2
It's 15
AND 2.
(I duuno what page it's from so I can't check the original... It's probably something about mistranslation or could be translated better though.
When you translate, you separate that portion into a part by itself instead of every single piece of articles everywhere all at once, so sometimes words stacked where they shouldn't... That reminded me of another case in early 3E over a decade ago. Someone argued with me about something something magic disease. I asked for the original page, flipped one page back, and there it was. (Tl:dr - Not magic.)
That guy
only translated that bit about that disease, and argued for it for a whole week, without even reading the overhead. Which was understandable, cause that's only how much a brain can focus on right that moment.
But... If you are really having a problem with something,
look for the original should be the first step you do if even you might not be the best in the other language, cause somebody else can check that too. v=3=v )