Holding packet energy fixed while count changes makes the input-energy ledger visible. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Two packets make twenty-four joules
Hold packet energy at 12 joules. With 2 packets, the cycle input is 24 joules.
2⋅12=24
Three packets add another packet of input
The packet value remains 12 joules. Three packets give input energy 36 joules.
3⋅12=36
Four packets make the count scale readable
With 4 packets, the checked total reaches 48 joules. Three rows make count times packet energy readable.