The UI file hard-codes the initial geometry to a size 256 x 306 pixels. What is probably happening is that your system has a larger font size or scale than that used by the book's author, so the widgets that contain text get clipped. When you click the "More" button and the widget expands dynamically, the dialog then automatically adjusts its size so everything fits. I think if you manually adjust the size of the dialog by grabbing the size handle (before clicking "More") you can get it to look normal.

Open the UI file in Qt Designer and resize the dialog until everything fits, then save and rebuild. Then the dialog should look as you expect.