Why does pulling the magic mouse across the screen enlarges ap to extreme? Email, internet, mostly google aps? How do you resize?

why does the internet page, calendar, email or any ap enlarge when I simply move the magic mouse over the screen
When using google internet pages, calendar, email and I move the Magic Mouse 2 over the calendar it automatically enlarges which is irritating. Is there an easy way to undo this? To get back to the original size that things were prior to moving the mouse over it?

Magic Mouse 2 - Silver

Magic Mouse 2 - Silver

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