issue with cacluation value ROW(row index )

Question

i have excel with some forumal like

=B9*(1-$B$4/(1+(ROW(B9)-ROW($B$8))*$B$5))

i can not get what does ROW(B9) - ROW($B$8) means also my calculation differs from excel outut due to calculation of ROW(B9)

Please exlain what does it mean

Answer 1

Row returns the row (as a number) of the cell in reference, or itself.

Working in cell D2:
=row() --> 2, but copy D2 to D3 and it gives 3 because now in row 3
=row(B9) --> 9, but copy D2 to D3 and it gives 10 because reference cell moved 1 row down
=row($B$8) --> 8, regardless of what row you are in. Copy from D2 to D8 and still gives 8 due to absolute reference ( $ )