A fixed disparity is 'one that was fixed earlier'. That means that we noticed a disparity, but when another guest recreated the same search we found the disparity had already been eliminated. That means it could go straight over to the Resolved tab - woohoo!
This situation sometimes occurs when you update your rates but it takes a little time for the new rates to go live on the OTAs. Please note you can also manually mark disparities are fixed if you know that the disparity is no longer 'active'.