Adding on to what others have already said about diff labs-
In addition to the number, one needs to know the units and the normal reference range for the lab where the test was analyzed. Without units, it is impossible to say if a "4" is low, normal or high. Even with the same units, different labs have different normal range because of variations in the way the test is done. It's useful to ask for a copy of your lab results; the paper should show your lab value and the normal range right next to it.
If you have enough tests, some values may turn up slightly low or high and still be normal since the normal range is the normal for 95% of healthy people, with 2.5% having values below and 2.5% having values above. Lab values that are quite a bit higher or lower than the normal range are more likely to be significant than values only slightly out of the normal range. Your doctor should be able to help you understand whether a lab value is abnormal and if so what it means.