When the numbers are long(i.e. bank card number), they get truncated to scientific notation, which makes them totally useless.
This is excel or your spreadsheet app of choice doing this, unfortunately. A CSV file isn’t modified by Bitwarden on import.
You can ‘import’ the CSV into an XLSX file (or similar) into ‘text’ columns to make any edits, etc. - re-save as CSV and import without opening again to keep this from happening.
Spreadsheep apps will also eliminate leading zeros, too 
What a load of crap. The file was saved as text and imported without loading into anything else. Maybe you make sure of what you’re talking about first.
Lloyd,
Trey is trying to help you. Even if he’s wrong, he’s making an effort to help you. You think people will help you with that sort of attitude?