Screen Start Code Not Working As It Should

I put an alert into my app that I’d only like to appear once (it’s a disclaimer that people don’t need to see all the time). I put it into a page and wrote the code as when the page starts, the alert shows. Then, it shouldn’t show up again. Despite that, the alert appears every time I open that page. Can someone help me out? I will attach a picture of my code.

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