Invoice taxable amount 4,287 times higher than it should be

An invoice was entered against the wrong PO by mistake, and paid.  A correction invoice was entered to "move" the funds from one PO to another.  This correction invoice, it was noticed later, had tax rate variances of over $1 million, even though the PO amount was only $440,249 and the matched amount was $23,171.  In the tax details > detail tax lines of AP invoice workbench, we see that the taxable amounts are extremely high, for example 99,360,144.38.  Where did these extreme numbers come from?  The taxable amount should have been $23,171.  $99 million is 4,287 times higher.  How