It's just that "commie metric" thing. A calorie is the amount of heat it takes to raise a gram (or CC) of water one degree centigrade. They are saying a square CM of the suit can handle that amount of heat. For the real layman that is really just a number that you use to compare different suits.
a "calorie" is the amount of energy needed to raise a gram of water one degree, a "Calorie" is actually a kilocalorie or 1,000 calories, the capital "C" imakes quite a bit of diference. if it helps you put in perspective one calorie is equal to 4.18 joules
Even in France, inventors of the metric system in the 18th C., you can still buy vegetables in livres [pounds], firewood in cords and threaded plumbing items clearly labelled in BSP/ANP. My bar has pint glasses. The BTU is still used to measure heat worlwide. As it happens my size 11 boot measures [and holds] exactly 1 foot & my hand is 4" wide. We still measure by the mile and the knot in the UK. Windspeeds are still quoted in Beaufort Scale, [based on mph]. As to the old gram-second-centigade units- they are deader than corduroy: SI units in metric were adopted well over 30 years ago. But imperial measure persists. Why? Because for the man in the street the metric system is a half-baked idea cooked up by intellectuals. Not, you will note a 50% idea, but a good ol' fraction!
I think it would be really far out if someone made the standard unit of measure 1/10,000,000th the distance from the north pole to the equator, as it passes through Paris. This just totaly makes sense. Anything else is just arbitrary