don't worry even faint line mean you pass, for lab standard- 50 ng/ml EMIT initial test, 15ng/ml for GC/MS confirmation test
they run GC/MS if initial come positive or if the company order the test pay for, for example if the test is for job. If the lab is certified will use this standard.
btw if you look for real answer ,morning urine have the highest concentration, ..so go to take your test at the evening,