The reciprocal-map spot is a projected source address, not a free label. 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 displayed spot is only the projected address
The reflection ledger records all three Miller indices, while the training map displays the projected pair.
(h,k,l)↦(h,k)
Three families keep the projection source-bound
Changing the hidden third index can change the spacing without changing the two-dimensional rule.