PE 15: Why doesn't the custom print size print out the size I want?

I have spent 3 hours trying to print some pictures for my daughter.  Some came off her phone and some from a camera.  She's making a scrapbook and has different size requirements.

I've set up custom print size (as an example) Height 3.5 x Width 4.5.   When I print, the actual size after printing is almost always much less, like 2.25 x 3.5 (or something else).   Why aren't the printed pictures coming out the size I designated?