According to the description on the back: 1 cap in the tank.

Since 1 cap corresponds to ~50ml, and the tank holds a good 5 litres, this results in a mixing ratio of 1:100.

To answer the question: 1 litre of water to 1 ml of cleaner.

At least my X40 Ultra Complete has a compartment for the detergent, i.e. nothing is mixed by the user, but the compartment is only refilled from time to time (I slowly but surely used up the first litre after a year)