Insurer valued my totaled car at $4,200 less than every comparable listing I can find - normal?

Got rear-ended pretty badly three weeks ago. The other driver was 100% at fault and their insurance accepted liability. My car got totaled - 2019 Honda Civic with 61,000 miles, one previous owner, good condition. Their insurer came back with a settlement offer of $18,300. When I started looking at actual comparable cars for sale in my area I'm seeing the same year, similar mileage, similar trim going for $22,000 to $23,500.

I asked the adjuster to explain how they got to $18,300 and they sent me a valuation report from a third-party company called CCC Intelligent Solutions. The report lists "comparable vehicles" but when I looked them up, some dont exist on the dealer lots anymore, one is listed as sold, and one is 40 miles away in a different market. They also applied a "condition adjustment" that knocked off about $800 with no real explanation.

Has anyone successfully negotiated a higher settlement? The adjuster told me I can provide my own comps but I don't know what format they want or how much weight they'll actually give them. I need this money to buy a replacement and I genuinely can't find anything comparable at what they're offering. Is there a process for formally disputing the valuation or is this just how it works?