Start with the number that reframes everything
Five healthy people in every hundred fall outside a reference range on any given test. That is how the ranges are built, not a flaw in them. On a long panel, at least one flag in a healthy person is more likely than none.
Every page in this section follows from that. A flag is a comparison, and the work is deciding whether this particular comparison matters.
The four questions
How far outside, in which direction, next to what, and compared with when. Those four settle most reports, and none of them is answered by the letter printed at the end of the line.
If you have a report in front of you now, the upload block on these pages sorts your own lines by what deserves attention, against the ranges your laboratory printed.