A reflection row is accepted only when spacing, wavelength, and map sources agree. 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 reflection row cites spacing and wavelength
The audit carries spacing 5 m and wavelength 6 m.
d=5mλ=6m
The reciprocal map remains the same source
The reflection's map source is the one with projected spot 2,2.