Thank you for bringing this indexing error to our notice.
You will know that at the moment it is not editable, but we are told that those records at present in this condition will eventually be editable.
See this Article in the Family History blog: Editing Dates and Places on Indexed Records—FamilySearch Update which includes the phrase: "Note that this feature may not yet be available for all indexed FamilySearch records, but it will be available in the coming months."
So we can only ask you to be patient. I have reported this, in case anything can be done about it now.
I hope that this helps or that it can be fixed sooner!