The formula with 3.3 substituted
miles = 3.3 ÷ 1.609344 = 2.051
The constant is an exact definition, not a rounded factor: the mile is 1.609344 km, the US gallon is 3.785411784 litres and the imperial gallon is 4.54609 litres. The Kilometres to Miles Converter explains where each comes from and gives a longer table.
At a walking pace of 5 km/h, 3.3 km takes about 40 minutes. At an easy running pace of 10 km/h it takes about 20. In metres it is 3,300.
What 3.3 kilometres means in practice
3.3 km is 2.05 miles, just over the two mile mark. It is around eight and a quarter laps of a track and a common distance for a beginner's run-walk session of about 25 minutes.