This interesting, according this aritcle
http://www.mmaweekly.com/absolutenm/...=485&zoneid=13 Marquardt tested with 49 ng/ml in his A sample but tested below the 6 ng/ml in his B sample. There was an 8-10 day span between the A sample and B sample being taken.
Either NA from supplements leave the system faster or they messed up the testing. There was an incident before in which a WADA tester did not properly refrigerated the sample, which caused the NA level to increase. I guess that's why they test you twice and Sherk testing positive for both leaves him with very little excuses.