The description column in Factory Talk View ME doesn't pull information from the PLC. It's just for you to enter descriptions in the ME software if the tag name doesn't describe what the tag is. More helpful for SLC based applications that use data table addresses instead of tag names.
If you need to have those descriptions populated with the descriptions in the PLC, the easiest way is export the tag database to an excel document (CSV). Do the same with your PLC tags. Open both documents and copy the descriptions for the PLC export into the HMI export. After you're done, import the HMI tag document back into your program and tell it to overwrite existing tags. This should populate the tags with the description, but you might want to back the program up to an .APA before you try it just in case.
There might be an easier way to do this, but I don't know of any.