Here's a breakdown:

* mA: Stands for milliamperes, which is a unit of electrical current.

* 400mA: Indicates the amount of current the light bulb needs to operate.

Important Note: This is a measure of current, not power. The actual power consumption of the light bulb (measured in Watts) depends on the voltage of the electrical supply.

To calculate the power, you would use the following formula:

Power (Watts) = Voltage (Volts) x Current (Amps)

For example, if the voltage is 12 volts:

* Power = 12 volts x 0.4 Amps (400mA)

* Power = 4.8 Watts

To summarize: 400mA on a light tells you the amount of current the bulb requires to operate.