When you have a certain number of LED luminaires the required wattage is the sum of your Nimbus luminaires multiplied by the indicated power consumption.
Example: If you have one Nimbus luminaire with 4 watt power consumption you will need a Nimbus converter with (1 luminaire x 4 W =) 4 W or more.
If you have six Nimbus luminaires each with 8 watt power consumption then you will need a converter with (6 luminaires x 8 W =) 48 W or more.