On an iPhone in Safari, certain font sizes appear to be magnified.

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This may be due to the "Zoom" feature being accidentally enabled. You can try to disable it by following these steps:

1. Open Safari on your iPhone
2. Go to the website where the font appears magnified
3. Double-tap the screen with three fingers

This should disable the Zoom feature and make the font appear in its original size. Alternatively, you can go to "Settings" > "General" > "Accessibility" > "Zoom" and make sure the toggle switch is turned off.