When vertically justifying a table; setting <?tbrivjb=1> gives a way of controlling the amount to expand a row, by calculating the amount by which the contents of the row need to expand. PTC ALD does this by inheriting the paragraph bottom VJ margin from the last line in the cell (which would otherwise be ignored), and using it in addition to <?tbvjmrowb> and <?tbvjprowb> to add space below the text for the cell, but inside the cell boundary.

Using <?tbrivj>, <?tbrivjb>, <?tbvjmrowb> and <?tbvjprowb> together enables you to ignore the table and row boundaries and justify the content as though the table didn’t exist. This gives a more even spread of the extra space over the page. This is particularly intended for slim tables, when they’re being used to simulate columns.