A long time ago (in the 1970s, for example) the
rule for forming plurals from letters, numbers, symbols etc. was
done by adding an apostrophe—cross your i's; make your
3's clearer, for example
Nowadays, however, the plural is most often
formed without an apostrophe: ATMs, 3s, and so on. Times
change! The apostrophe should be reserved for showing possession.
In this case, the newer rule makes more sense.
See our most