nT is nanoTeslas, a measure of magnetic field.

The purpose of airborne geomagnetic testing was to get a detailed geological map of the area structures.

KXL has explored some of the Golden Mile e.g. by trenching and surface sampling, but before committing to drill holes sites, they wanted to know the overall shape of the surface structures - very wise.

It also confirms their land-claiming / rights decisions.  Really that is what the stock is trading up on today - there are no drill results.

By the way, nT (nanoTeslas) are a very, vey tiny meausure.  The MRI machine at your local hospital produces a field 1 billlion times stronger (okay, in a small area).  Even the earth's rather weak magnetic field is in the region of 10,000 times stronger.  We are lucky to live in times where this kind of instrument exists.