If I read it correctly the following would suggest the margin of error saves a positive being recorded.
As a consequence Harness Racing New Zealand (HRNZ) and New Zealand Thoroughbred Racing (NZTR) have prescribed, within their respective rules, levels, which when exceeded are considered a breach of the rules. The threshold level for an offence being committed is 36 millimoles per litre of plasma. There is a margin of error of +/- 1.00 millimole per litre of plasma.