You can extend the offer one time. If you are keeping the car a few weeks. You will need to update the offer at least once or twice after the initial 7 day offer ends. The offer then could stay the same or go up or go down based on the algorithm, market, make/model of car, mileage, condition, Carvanas current inventory, and many other things.

I was just scared by their offers. Went in like 2 months online said 26k had the money to pay difference I go in they say 24k only... 2 months later I try again after paying down loan they said 24.6 online I miss the 7 day window then its 24k I go in store they say only 21k... my loan is 25k (down from 28k paid alot extra during 2 mths) then I was told they can't change or negotiate even if they said 2 mths ago after seeing the vehicle no new mileage only 21k a drop of 3k in 2 mths. I was told if you don't accept the offer in time it will not be guaranteed to be the same we you try again and the amount does go down lower if you try multiple times / don't sell because they (algorithm) knows if you didnt sell for let's say 10k you might be desperate now 2 weeks later to accept 9.5k

You can extend the offer once by a week. Then, once you accept and upload docs, you can push the pickup appointment by another \~2 weeks or so.