Occupancy is the seen hit count divided by the available channel capacity, giving a finite-cell fraction that signals how full a detector layer is. The 4 seen hits over 8 channels give occupancy 1/2 exactly for the stated capacity ledger; real occupancy carries dead or noisy channels, threshold drift, pileup ambiguity, clustering choices, alignment error, readout inefficiency, and finite-count uncertainty.
Occupancy uses the same checked detector capacity. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Occupancy cites the same detector capacity
The seen count 4 is measured against 8 available channels.