I have a mid '80s Miyata 710 that I am trying to make more upright for an upcoming trip to ride the Katy Trail in Missouri.

I have found an extra long Quill stem I think will fit, but I just can't get the measurements to match.
The one I want to buy is listed as "22.2mm quill with 110mm reach. Bar clamp is 25.4mm". When I measure with calipers I get the stem width at .7 inch which is (if I can do the math correctly) is 17.7 mm.
The bar width is correct at 1 inch = 25.4 mm.

So am I just measuring the wrong thing, and this is really the correct size?

Thanks for any help. I need to buy this soon!!