When I was using my 5770 I got the usual 7.4. Also ran the W.E.I and got either the usual 7.4, or 6.1. It was hit or miss after a
driver update. Couldn't tell you why it did it, but it did it frequently. Usually if I ramped the fan up on the card while I ran the W.E.I it would go back to 7.4.
If you wanted, you can delete all the XML files inside the Datastore folder, and re run the assessment. C:\Windows\Performance\WinSAT\DataStore
Only the files
inside the Datastore folder though. Sometimes that clears little glitches with running it.