Catalog duplicates with different Bulletin IDs

Hi,

Can anyone explain to me why both the following exist within the Client Catalog with seemingly the same version of the software, but with different Bulletin IDs, slightly different file sizes and different latest updated dates? Neither of them are expired.

https://www.dell.com/support/home/uk/en/ukbsdt1/drivers/driversdetails?driverId=JT5W8

http://www.dell.com/support/home/uk/en/ukdhs1/drivers/driversdetails?driverId=M6NJD

I've seen this quite a lot and it's pretty confusing.