Mold reports that differ so greatly.

March 4 I had a mold reading done and it came back as crawlspace elevated with a reading of 16,912. On March 8, landlord had a reading done and it came back with crawlspace reading of 210. I did not believe this report, so I called in another company on March 19 and readings in crawlspace came back at 12,480. How could landlord’s reading be so low when two readings I hired reputable companies to do came back so high?