If your cluster shows full after a few minutes then, it's normal.
The fuel level sensor signal is dampened by the cluster so your fuel gauge doesn't bounce up and down on inclines.
If it bugs you, your dealer can change the instrument cluster version coding to "direct sensor value".
This is only for ML's.
Dr.D

__________________
Dr.Diesel -
Shop Foreman
Master Guild Mercedes-Benz Technician.

Think the dealer is expensive? Do you know how much it costs to train a dealer tech? Or buy the required MB special tools to have on hand?