Hello
Cells.FileFormatType.Numbers
vs
Cells.FileFormatType.Numbers09
Both have the same description:
Enum FileFormatType | Aspose.Cells for .NET API Reference
Any info? The difference? Why 2? 
Yes, we noticed the issue with the description/text which is repeated for both format types. We will update/fix it soon.
Please note, .numbers file is a spreadsheet file created by Apple Numbers which is a spreadsheet bundled with macOS and iOS. A numbers 09 file is a spreadsheet file that can be opened by Numbers 2.0 through 2.3 on a Mac, it is an older format that may not support some features of the newer versions of Numbers.
Hope, this helps a bit.
As we already noticed the issue with the description for the Numbers and Numbers09 enumeration members, both have same description/text, so we will log a ticket to fix it.
We have opened the following new ticket(s) in our internal issue tracking system and will deliver their fixes according to the terms mentioned in Free Support Policies.
Issue ID(s): CELLSNET-53581
You can obtain Paid Support Services if you need support on a priority basis, along with the direct access to our Paid Support management team.