I'd interpet this as meaning that the anti-doping laboratories got a result that was 400 times that of the UCI result, ie. 20,000 picograms.
Of course, this leads to the problem that "400 times less" therefore means 400*50 times less, which is 20,000 picograms less, therefore 0. So the real antidoping lab reading should be 20,050. This doesn't make a big difference when you speak of "400 times less", but "three times less" is a real problem.
Put simply, if x = a*y, then y != x-(a*y). y = x-(a*y) + y.