Both the samples A and B are taken at the same time. This is due to the reason that the test results for the A sample are taken in different conditions and times. There could also be a possibility that there could be inconsistent results with 1 sample. The B sample tested will confirm that the A sample was correct. If there is a vast deviation then the benefit goes to the offender like what had happened in Jyotirmoyee Sikdar's case in Asian games, when she was tested positive for the A sample but due to the deviation in the B sample, she was cleared and she got her gold medal back
