As Jersey says, your vet could’ve meant the mixing ratio. It’s one volume part CC to 2 volume parts water. As you are well aware, a 4.38 kg rabbit needs more than one tablespoon dry matter per day, Oxbow says:
“Generally, for a herbivorous mammal, the amount is 3 tablespoons of dry product or 50 ml of mixed product daily per kilogram of body weight. A weaker animal should often be given more frequent, smaller meals.”
This page contains excellent instructions and has amounts and portion-sizes according to weight: http://www.oxbowaustralia.com/critical-care%E2%84%A2-information-for-pet-owners/
That said, the amounts stated by Oxbow are very generous and it can be difficult to get that much CC into a bun. It’s great that your girl is willing to eat craisins and kale, and because she has that little bit of appetite, you might be able to find some baby fruit/berry smoothie or pure she´d like and mix the CC with, to make it yummier and maybe inspire her to eat it from a bowl or teaspoon, like Jersey says.
The most important thing for now is to get good nutritious food into her. You mentioned before that you had had blood work done and it was fine. Most bad systemic illnesses would cause anomalies that can be picked up in blood works and there was nothing, so hopefully she’ll get through this with your god care.