Adjuster offered me $4,200 for my car - KBB says it's worth $9,800. What do I do?

My car got rear-ended two weeks ago by someone who ran a red light. Their fault, 100% on camera. Their insurance accepted liability no problem. Then came the offer.

$4,200. For a 2019 Honda Accord with 61k miles, new tires last fall, and zero accidents before this. I pulled KBB, Edmunds, and even searched listings on CarGurus for comparable vehicles in my area. They're all coming back $9,500-$10,200. I even printed out eight comps and sent them to the adjuster.

She came back saying their system shows the market value at $4,200 and that's their final number. She mentioned some "condition adjustments" but wouldn't explain what they were. I'm not a lawyer and I don't know if I need one, but this feels like they're just hoping i'll take whatever they offer and go away. Anyone been through this? What actually worked?