daily cash adjustment impacted by iPhone trade-in

I recently bought a new iPhone and received a $120.00 trade-in amount for my old iPhone 8 that was subsequently credited on my new Apple Card. However, my balance was then adjusted up by $7.20 or 6% - the Apple Daily Cash feature this month - of $120.00.

To me, this means that my trade-in is not worth $120 but rather only $112.80 and not treating it as a separate transaction. I just don't think that's kosher - it's not the money obviously - 7 bucks - but more the principal.