Google says "duplicate store codes" when updating the hours of operation of hundreds of shopping sites via CSV

I am trying to change the hours of our pitches (206 pitches). The hours will all change the same for all stores. I have uploaded our locations to CSV, made the changes, but when I try to upload them, it indicates that it has duplicate store codes. Has anyone ever done this? I read on Google documents that bulk editing was available.

Does anyone have a step by step for this process?

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