Note that all heavy cream has carbs, approximately 6g carbs (lactose) per Cup or 8 Fluid Oz, so 0.375g per Tablespoon. So it's 12 to 15g carbs per Pint depending on American or Imperial/UK Pint...

It's 'technically' only zero grams carbs per serving if the Serving Size is small enough (e.g., a Tablespoon or 15mL) to have less than 0.5g carbs (e.g., 0.375g).

So you need to add between 12 and 15 grams carb to your recipe for the cream alone, depending on what size pint you have.