Just FYI, the 10G ports on a QFX 5100 running latest JunOS are being reported with a speed of 4.29Gbps, which I assume is likely the actual returned value being constrained by a 32-bit container?
Not a critical thing for us to fix - I was actually disabling polling for all of our Juniper vcp stacks in Observium (most of them take > 300s to complete a polling cycle) but noticed this as I was going through them and figured I'd pass it along.
Cheers,