Yes actually it is Newton and yes it is 28kg (easiest is 10N = 1kg). And it isn't that 275N can only give buoyancy to a 28kg (61.6 lbs) heavy person, but is the force/weight needed to turn a person over in the face up position (by ISO standard). Buoyancy and the ability of turning a person over has a lot to do too with what is being worn, salt water or sweet water, weather conditions, etc, etc. Furthermore one should not forget that the weight in air is different from the weight in air (submerged in water weight loss = object in air/specific gravity). Furthermore you may want to get a refresher in your water drills, cause you should know what to do with your kit (60kg) when in water.