Many laboratory results come with a reference range: values established by studying groups of healthy people. It helps interpret a result, but is not a perfect dividing line between health and disease. A healthy person can have a result outside the range; someone with a health problem can have one within it.
Ranges can vary with age and with the methods used by a laboratory. Food, medicines and how closely pre-test instructions were followed may also affect a result.
To interpret it, a clinician considers why the test was ordered, symptoms, medical history and any earlier results. A flag deserves attention, but cannot establish a diagnosis on its own. Reading the number in context is more useful than searching for a universally ideal value.