On a HiDPI screen, Spectacle starts out with the window so small that some labels are cropped: http://qwertty.com/tmp/spectacle-tiny.png It should be bigger so everything is readable and well-spaced.
Can you give more details, like the version of Spectacle, Qt and your distribution? Have you tried git master? There should be some fixes for HiDPI. Probably not the window size, but maybe you are lucky.
Git version works fine, thanks.
*** Bug 386201 has been marked as a duplicate of this bug. ***