All the Mac screen resolutions are that same aspect ratio (because Apple). After some fiddling, it snapped into a size that looks correct (with lines that fit the words) and now it defaults to it every time I run it (because Apple). If the game is so sensitive to screen ratio (only 20% of screens are 16:9), you can ask Unity to force that ratio on every screen (it letterboxes it). Thanks for responding. Good game :)