The filled boundary case has zero empty slots. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

The same slot ledger can be completely filled

The toy band again has 8 slots.

slots=42=8slots=4\cdot 2=8
Filled band slotsEvery displayed count is checked.sites=4statesPerSite=2electrons=8slots=8filled=8empty=0occupancy=filled

Eight electrons fill all eight slots

The filled count is 8 and the empty count is 0.

filled=8,empty=0,occupancy=filledfilled=8,\quad empty=0,\quad occupancy=\mathrm{filled}
Filled occupancyFilled means no empty slots in this toy ledger.sites=4statesPerSite=2electrons=8slots=8filled=8empty=0occupancy=filled