I have Word 2010 but this particular set of options has been the same since Word 2010 according to the Microsoft documentation. When I get to the Autoformat as you Type Tab, the following options are listed under the Apply as you type section as checkboxes in two columns:
Automatic bulleted lists
Built-in Heading styles
Automatic numbered lists
I am presuming you wish to turn off automatic numbering permanently, though you can, of course jump back in to that dialog again to turn it on. I'm guessing that your not seeing the Automatic numbered lists might have something with how the screen reader is traversing the options in that dialog tab. Try either searching for Automatic numbering using the screen reader search function or just brute force tabbing your way around until you land on it. It has to be there somewhere because they always make a distinction between bulleted lists and numbered lists.
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