How do i know witch devices did i authorised?

There is no way except to check your Macs.

asanto wrote:

How do i find the names of the devices that are authorised for iTunes

"Devices," such as iPads and iPhones, do not need to be authorized at all. Only computers count in the limit of five authorizations.

Some people think iTunes should produce a list of which computers are currently authorized, like "Mom's laptop, Susie's Macbook, and the Dell Dad s**t-canned last year." Alas, there is no such list.

If you are at the limit of 5, use the "Deauthorize All" command, and then re-authorize just the ones you are still using.