A dilution standard is accepted only when it cites the matching threshold row. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
A standard row cites its amplification table
The first standard cites the threshold row whose start is 64 and threshold cycle is 0.
Ct=0
Equal-looking numbers are not enough
The source ref names the threshold-check slot and the field thresholdCycle.