This is how some people order food at restaurants (especially Chinese and other ethnic restaurants). Sometimes it's because the menu is written in an indecipherable foreign language, but sometimes it's because that person's afraid of horribly mispronouncing something. Don't be. That's what the English transliteration is there for. No one will spit in your food if you pronounce "Pho" like "pfoo".

These days, fast food places like McDonalds and Togos also have people order by numbers too. At McDonalds the numbers are for fixed menus. At Togos, all sandwiches are identified only by number. I suppose this makes it easier for the workers.