You need to sync the configs in RME. Perform a Sync Archive job, and check the "Fetch Startup" box. That will cause RME to fetch both the current running and startup configs from the device. If there truly are no differences, then the out-of-sync entry will go away.
That said, there are some known issues with out-of-sync between running and startup, so if the entry remains even after a successful Sync Archive, then you will need to post a screenshot showing the differences RME is detecting.