How can I compare the numbers within the transaction narrative with the credit or debit amount?
You can use one of Excel's text formatting formulas to identify whether the credit or debit matches the numbers in the transaction narrative exactly.
An example to get you started with the necessary formulas is shown here:
=IF( ISNUMBER( SEARCH( TEXT(B3,"0.00"),A3 ) ),"yes","no" )
Where, B3 contains the amount and A3 contains the narrative.