In the License Manager under Certificate details/Licenses: it indicates 2.
Under USB Flash Drive Export: it indicates "Enabled, Never Expires, Licenses: 5"
Are they different licenses? I think I've got the "2" from the description in the Certificate Status window, "... installation on up to 2 computers ..." but I'm unclear on the "5" in the USB section.

That means you added on 5 USB export licences at some point, which grants you the right to export Opus to 5 different USB sticks, in addition to your normal installs.

It may have been a long time ago, if you've forgotten doing it. You only need to pay for the USB licences once, and they then carry over each time you upgrade the program to a new major version for free.