Multiple energy packets contribute independently to the total cycle input, so the cycle budget is packet count times energy per packet. With 5 packets at 12 J each the cycle input is 5 times 12 = 60 J exactly for the stated toy energy ledger; real cycles have incomplete coupling, variable dwell times, heat loss, load dependence, and uncertainty.
Several identical packets form the cycle input energy. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.