Total loss payout

I had an accident on the 12th, the other driver accepted fault and my car was a total loss. Their insurance got me a rental car within a few days.

I had been waiting to be contacted by an auto damage adjuster (car was already towed to the salvage lot) and I got the call last Friday (12 days after the accident). The settlement offered was lower than what I was anticipating, so I asked for the report and I saw that they listed the wrong trim for my vehicle which lowered the value by a good bit. I informed them, and they said they would look into it and fix the issue. It's nearly been a week since then and I haven't heard back.

I know that I may or may not be able to speed up the process if I called a little more, but I'm just confused as to why it's even taking so long to begin with, because wouldn't they have an incentive to offer a settlement quickly given that they're paying for my rental car by the day?