Window resizing dimensions wrong

After resizing the window, it seems that the dimensions are consistently 16px too narrow and 8 px too short:

• 1280 x 720 actually resizes to 1264 x 712.
• 1280 x 768 actually resizes to 1264 x 760.
• 1200 x 800 actually resizes to 1184 x 792.
• 1920 x 1080 actually resizes to 1904 x 1072.