When a National-Bank statement you need to convert spans more than one page, Convert·Into merges every page into a single transaction table rather than treating each page as its own file. When a statement runs several pages long, the processor stitches the transaction table together end to end, so the header repeats do not create new table sections.
If the running balance on your National-Bank statement does not add up row by row, that is exactly the kind of mismatch Convert·Into is built to catch rather than pass through silently. Every statement is checked against its own printed closing figure. As each row is extracted, the running balance is recalculated; if a line breaks the sequence, that row is flagged for review rather than discarding the whole file.