How is your flatfile sample data looks like? can you upload the file? What is your RecordDefinitions and field definitions looks like??your comments above are lit confuse to give any suggestions.
the question is ambiguous ,but from what i can understand …i guess the fields length should be 18(xxxxxxxxx.yyyyyyyy) where y is decimal places.
or its a mainframe transformation description,usualy they do specify s9(8) x(9) in this format while creating flatfiles for mainframe …where s implies “signed” .
HTH
sri