A three-row scan shows how starting copies shift the first threshold crossing. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Three starts make three first-crossing cycles

The threshold stays 24. Starts 2, 3, and 6 reach at cycles 4, 3, and 2.

2433622\to4\quad3\to3\quad6\to2
PCR threshold crossingExact doubling pins the first cycle that reaches the threshold.c0=2c1=4c2=8c3=16c4=32start=2threshold=24Ct=4crossed=1accepted=1

The middle row is the original three-copy case

Start 3 gives counts 3,6,12,24,48, so the first crossing is cycle 3.

3,6,12,24,483,6,12,24,48
PCR threshold crossingExact doubling pins the first cycle that reaches the threshold.c0=3c1=6c2=12c3=24c4=48start=3threshold=24Ct=3crossed=1accepted=1

More starting copies move the crossing earlier

Start 6 reaches 24 at cycle 2, two cycles earlier than the low-start row.

4    2=24\;-\;2=2
PCR threshold crossingExact doubling pins the first cycle that reaches the threshold.c0=6c1=12c2=24c3=48c4=96start=6threshold=24Ct=2crossed=1accepted=1