On the .dpf document, "2024 Mustang (CZJ) Canada/United States of America, enUSA, Edition date: 202212, DOM" page 371, lists 10.0qt (9.5L). Obviously, Ford changed the capacity between the 2024 manual and the newest owners manual.
If you change your own oil, you have to buy 10 qts anyway. So fill 9 qts, measure, fill to 9.5, measure again; if you're still low (like my 2024 was) then fill to 10qts and measure again. Then, drive off into the sunset.
Looks like the strip of windshield I clear off when commuting to work in the winter. Least amount of ice removal possible in order to drive.
My commuter is not a Mustang, but I digress.
This is the obligatory reminder post: buy the DIYVan kit and live happy knowing you'll never have to deal with the weird hole in the fender, ever again.