it will be the same as if you were taking test. things that will affect it are the amount of prohormone you took as this will dictate how much was converted to test and how long ago you took it. for 4ad transdermally, i figure that 2 weeks should be about enough to clear out for a lighter cycle. remember that people who test positive for test are usually using esters which have halflifes of up to a month, but usually a week or two. even if it has a week long half life, it will show up months later as at week 4 after last inject you will have about 1/16 (really less than this because as levels get near physiological, the enzymes are no longer saturated and the breakdown is no longer exponential, but more linear).
remember 4ad has a short halflife so it will go faster. if you used 4ad-cyp, you may as well have used test cyp, at least testing wise as clearance time will be similar.
as for an excuse, well 4ad is legal in the USA, so you don't need a defence, unless you are participating in a sport where it is banned. if anything happens, like you get fired, i smell a big lawsuit.