This means that a student was assigned two SSIDs at some point and, when this was discovered, the two SSIDs were merged. Your error record has the merged (end-dated) SSID in the SSID field.
In a second browser, look up both SSIDs in SSID. Review the history to make sure that the merge was correct. (For example: The students are not twins or similar students.) If the merge should not have happened, contact the ODE Help Desk and they will "un-merge" them.
If the merge was correct , change the SSID in your error record to the other SSID and click "Save" to submit the record again.