Your test code breaks down as follows:

SAP = Substance Abuse Panel (Immunoassay screen)

5 = Five types of drugs to be screened

50 = 50 ng/ml cutoff limit for THC

GC/MS = Gas Chromatography/Mass Spectrometry (This test is only done if the sample shows a positive for any of the five drugs tested on the SAP screen)

Grab yourself a home THC test and test yourself with the first void of the day. If you test 'hot', you should consider subbing with a clean sample (or synthetic) since this is an employment-related test. If you somehow cant obtain a clean sub sample, then your only other option would be dilution. Read both the Dilution and Substitution threads in the sticky's.