The CCC numbers now are a different breed from the older RVIA numbers. The feds (NHTSA) developed their own standard, which manufactures are required to use.
Under the new standard, water counts as part of the CCC - in the old standard, it did not.
For example, a trailer with a CCC of 1200 lbs that is carrying 40-gallons of fresh water has used approximately 330 of the 1200 lbs. With the older RVIA CCC, the 40 gallons has not used any of the 1200 lbs, because the weight of a full tank of water had to be accounted for before calculating the CCC. In other words, a 1200 lbs. CCC with todays standards would be about 870 lbs. with the older standard.
Note: the number of occupants had no direct bearing on the CCC of a trailer, since occupants should not be in the trailer while it is traveling. The weight of the occupants in a motorized RV counts as part of the cargo.
Tom