The battery’s internal construction determines how much charge it will hold. It costs more to make a battery that holds more charge. Since warmer temperatures are approaching, probably best to forget about it. It sounds like the C version you have now holds less charge than the N version, but it will probably work ok in the short term. If you have trouble w/it not cranking the engine next winter, you can replace it then. Presumably you got a reduced price b/c of the C version. I purchased a battery at Walmart a few months ago, the higher charge capacity version was $100, and the reduced charge version was $50. I purchased the $50 version, and has been cranking the engine & working fine all winter. I expect however that the $50 version will conk out and need to be replaced sooner than the $100 version would have.