That is how that particular action is intended to function. Per the start of the description on that action: "Gets the next email message".
If you want to grab more than one message, it's recommended to switch to the Outlook VBO available on the Digital Exchange. (It's also a lot more stable.) Optionally, I've uploaded an alternate version of that VBO
here that will also allow for multiple profiles (among other things), like the VBO you're currently using does.
Edit: The other nice thing with either of these VBOs, is that you can supply a time range to pull from.
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Ami Barrett
Lead RPA Software Developer
Solai & Cameron
America/Chicago
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