It gives you a minimum and maximum amount to put in below the readout for how many miles you have left. The readout is in gallons. approximately 4.5 ltrs equal 1 gallonSooooooo........ because my brain doesn't do math...... when my thingy on the dash says 'AdBlue Range 1500 miles' how many litres of AdBlue do I put in without over filling the tank!!!!??????