W N L

It is a clinical abbreviation. It stands for 'Within Normal Limits'. It's a handy phrase. We take blood pressure readings and the client asks, "Am I normal?" And I respond, "Your results are within normal limits." And the client asks, "WTF does that mean?" And I respond, "Your reading is less than 140/90, If it were that or higher, I would have to take another reading on the other arm to compare."
Normal limits are used for lab values.
They are used to determine where a person is on the spectrum of weight... are you NORMAL, OVERWEIGHT, or OBESE? That is one of the most dreaded charts I know, for in order for me to fall into the so-called normal zone, I'd have to be between 125-158 (according to the National Heart, Blood, and Lung Institute of the National Institutes of Health).
I suppose in this day and age it's best not to say NORMAL and instead offer limits.