The Packlists / Packing Screen show the Unit of Measure names and descriptions as entered via Exporting and Importing Products or through direct entry on the webpage Products Units of Measure. So if your Products page doesn't match your Picklists / Packing Screen, its caused by having different product codes and descriptions on the Unit of Measures vs the main Products page.

See below example of mismatch; noting the different extra parts of the code and description on the Unit of Measure level. 

The reason this is possible is because the system can accept different products codes, descriptions/names and barcodes on the various different Unit of Measures due to operational need, ability to give pick/packers extra information without showing customers etc. It's a strong feature but can cause problems through accidental mismatch without meaning to.

To fix this, either do it one by one through the webpage view or in bulk via the export/import of products; through the webpage, go to the Product Page, then the Product Packagings tab, then the Measures tab and finally use the Edit button on the right to change the code or description as necessary to fix the mismatch and have both screens read correctly.

Via the bulk method; follow the Exporting and Importing Products information and you are specifically looking to match the Products section on the left of the excel spreadsheet with the Unit of Measures on the right side of the spreadsheet. Then success your Packlist and Packing Screens will display what you are expecting!