I change the frequency of dosing and the size of doses based on how sick we are--so there's some guessing involved.
Early on, I had to write down doses--time & amount. If I was fairly sick, I may take more every hour, and see if I hit bowel tolerance throughout the day--may increase the size of the dose after a while.
The rough guideline I've read is 250mg/kg body weight, spread throughout the day. That's 1.1 grams per 10 lbs body weight, but my kids and I always needed far more than that.
The kids and I get diarrhea if we take too much, some people get gassy and feel rumbly, so consider either.
For really acute illness-when I had mastitis, for example--I dosed every 20 mins and finally got diarrhea, and then my fever went down and my body aches stopped--the end was pretty abrupt. But for more normal illnesses, the end is more gradual, you'll slowly start to feel better, the amount of vitC you need will drop more slowly.
You want to stay just a bit under where the diarrhea/rumbly stomach occurs, you don't need to be higher.
Hope you feel better soon!