C / c = kcal?
or
C / c = carbs?
I’m assuming you’re using C & c interchangeably to mean kcal right?
If so, then 800kcal ride probably means you should be eating somewhere between 200-350g of carbs over the course of the day, depending on goals, activity level, etc.
Regardless, answer depends on duration of workout.
If you burn 800kcal over the course of a 2-hr ride, you’d be better off having a higher percentage of your day’s carbs intra-workout, than if you were to burn 800kcal in under an hour. Could have a very light breakfast and do most of the fueling intra-ride.
If you’re hammering the power and workout duration is shorter, it makes more sense to put a good chunk of your carbs pre-workout and post-workout, and not bother targeting anywhere near the upper tolerable limits of carb consumption during training.
Exercise duration is a primary driver for carb consumption rates.