Hi Juli! From what I read your body can absorb more than 10mg a day. If you check out the doctoryourself.com website, he gives a lot of research done into vit. C and that during times of illness you should increase your intake.
I'm not sure about the supplement you are referring to, but Vit.C should generally be taken with calcium (or a food containing calcium) for better absorption into the body. Someone else here may have more information for you.
As every person's body is different and its need for Vit. C may differ, try slowly increasing your vit. C intake daily until you exceed your absorption level. You will know this when you get the runs. Vit. C not needed by the body is usually flushed out when you urinate.
You might want to get pure absorbic acid in tablet or powder form and just use that for awhile. And you may want to try taking half a dose in the AM and half in the PM. It's also recommended to take Vit. C before exercising, as Vit. C is an antioxidant, and will help your body flush out toxins. This is word of mouth information from someone else, so I have no reference material to back it up.
It's also close to impossible to get the amount of Vit. C your body needs through fruits and vegetables alone, which is why a supplement is important.
Are you or someone you know suffering from a chronic illness?