Surely the answer is: Anything you like 
Maybe better visualised as this, a sliding window, so eventually the offset position = zero
then if a 'cell' C = (space + line)
the "equivalent" number of cells = the integer of 'window width' / cell (I)
remainder of space S = 'window width' - I x C
total of space = I x space width + S
Maybe better visualised as this, a sliding window, so eventually the offset position = zero
then if a 'cell' C = (space + line)
the "equivalent" number of cells = the integer of 'window width' / cell (I)
remainder of space S = 'window width' - I x C
total of space = I x space width + S