[Product Question] Why do some straw hats with noticeable holes in them claim to be UPF 50+?

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I’ve noticed some hats that clearly have holes in the brim often say they are UPF 50+. What’s up with that?Here is an example: https://www.amazon.com/Lanzom-Womens-Bowknot-Straw-Foldable/dp/B06XXXQXLN/ref=sr_1_9?keywords=Sun+hat&qid=1553120950&s=apparel&sr=1-9
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Submitted by The_Diviner