route identifier field in event table

I have an excel spreadsheet that I am trying to use as an event table to display types of underwater bottom cover. When I use the "Make Route Event Layer", it asks for the "Route Identifier" field. The route feature class so far has only one polyline in it, with an Id field of 0. I therefore made a field called "ROUTE" in the event table that is filled with zeros. I have tried formatting the cells as both number and text, and each time I try to set the "Route Identifier Field" of the event table to "ROUTE", it says:

"ERROR 000840
The value is not a Route Measure Event Properties."

I have also tried saving the data as a comma separated text file and it did not work. What exactly is supposed to go into the route identifier field? Isn't it the value that assigned the measure to an individual linear feature?

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