Family Shared Music authorization issue on multiple devices with older tracks

I am having a problem with authorising some Music tracks in our Family Shared Music. There are 2 of us. I have 3 devices authorised - 1 x Mac, 1 x iPad and 1 x iPhone. Wife has 4 - 1 x Mac, 2 x iPad and 1 x iPhone. The Mac is a shared device with each of us having a User account set up.

Several tracks purchased by wife a long time ago cannot be authorised as, apparently, they are authorised on more than 5 devices.

Is the system counting my 3 + her 4 as 7 in total?

Newer tracks don't have this problem. I will be checking to see if they are on all our devices.

[Re-Titled by Moderator]

Original Title: Family Shared Music authorisation