The M.mycoides genome contains over a million letters of genetic code and current DNA-technology can string-together perhaps a few thousand units in one go.
The method allows for many combinations that can mean many different pitches, and after the coach calls a string of numbers and the catcher deciphers the code on his grid, that sequence won't be used again for the rest of the game and maybe even the rest of the season.
Anyone who's heavily invested in the Mac ecosystem knows Automator, a built-in tool that can string together multiple computing actions without having to know a lick of code.