An online valuation is a quick estimate. You enter your car's make, model, year, variant, kilometres driven and a self-reported condition. A tool returns a price or a range. The system is useful for setting expectations, but it is working blind. It has not seen your car.
The final offer is made after someone inspects the vehicle, verifies the paperwork, and matches your specific car against current buyer demand. That is why the final number can land above, below, or near the online estimate. The estimate answers what a car like yours is roughly worth. The final offer answers what your exact car is worth to a buyer today.