Hi wxy,
A cholesterol level of 5.2 tells you next to nothing about heart disease risk. It says nothing about the relative proportions of LDL and HDL levels, nor does it tell us anything about triglyceride levels. These are much more informative.
For example, it would be quite possible for 2 people to have identical colesterol levels of 5.2 and yet one could have low CHD risk and one high risk. The person with the high HDL and low LDL would have very low risk, while the one with low HDL and high LDL a high risk. The total cholesterol level might be identical.
Similarly, a cholesterol level of 4 is not necessarily better than 5.2, unless the HDL / LDL proportions themselves are better. Cholesterol levels are fantastic at boosting statin sales however.
All the best,
fergus