Every browser (like Chrome or Safari) handles printing a little differently. To ensure all your tests fit perfectly on one page, you can use the "Test Full Layout" button.
This will show you all 16 test slots. Use your browser's print preview window to adjust the scale and margins until all the boxes fit on a single page. You don't need to actually print this test page.
Important: Once you find the right settings, remember to use them for all your prints to guarantee perfect alignment.