README.TXT: Documented that if the row-based and column-based imports produce different inserted row counts, this usually means that a table is underconstrained (the unique indexes don't cover all possible rows). The inserted row count difference occurs because column-based import collapses empty table rows into one insert, while row-based import performs an insert of the empty row for each input row. Without a unique index to combine multiple row-based inserts, extra rows will be added.