MA is an abbreviation for Mechanical Advantage. It describes the ratio of force input to force output.
Consider a lever that has a total length of 5 meters. Place the fulcrum of the lever at 1 meter from one end. The ratio between the length of the two ends of the lever is 4-to-1. To lift a mass of 4 kg positioned at the end of the short side requires a force equivalent to 1 kg on the end of the long side.
Force isn't actually measured in kg. The force required to lift 4 kg against earth's gravity is approximately 40 Newtons. And the force supplied by a 1 kg mass would be about 10 Newtons.