If you're watering it 3 times a week, which has 7 days, you can create an equation to estimate how many liters of water to give it each time.
[tex]\frac{7days}{3daysperwatering}[/tex] = 2.33
[tex]\frac{2Liters}{2.33watersaweek}[/tex] = 0.86L of water everytime you water the plant