The water is the vast majority of the overnight weight loss. pCO2 of 40 mmHg is normal. Resting tidal volume is 500-600 mL, and a breathing rate of 12-14 (officially 10-20, but really, more like 12-14). I'll let someone calculate the mass of CO2 exhaled in 8 hours.

The article claims that 200 grams/day lost as carbon in CO2 is typical. (The oxygen comes from breathing in, so doesn't count for anything.) That implies that the amount lost in eight hours of sleep is somewhat less than 67 grams.