Whilst some applications may require the use of additional material, the minimum amount of material to be used per square metre is 1.5 litres. This is generally sufficient for two coats but usgae / coverage is dependent upon the type, nature and porosity of the surface.
In waterproofing, 2 coats are a minimum but 3 coats are better than two coats and so on - provided that each coat is applied at about 0.5mm thick.
Your dry film thickness of the membrane must be at least 1mm but preferably 1.2 to 1.5mm.
It is important that you refer to the product data sheet and labels.