The capacity of the E70 N55 is 10.9l or 2.87 gallons.
If you are that peculiar you can flush it with distilled water then drain (now you have distilled water in your system) and add 1.44 gallons of undiluted coolant then fill the rest with distilled water.

COOLANT, COOLING SYSTEM TEST N55 > 17 00 COOLANT, COOLING SYSTEM
TEST
COOLANT, COOLING SYSTEM TEST SPECIFICATION
Coolant volume with integrated air conditioner AT Liters 10.9
Top-up quantity of coolant in the event of repair with disconnected coolant hoses.
Observe the mixture ratio and filling level! See RADIATOR -- OPERATING FLUIDS .
Liters 2.0
Test pressure for cooling system (excess pressure) bar 1,5