Reminds me of school back in the day when calculators were just becoming affordable. You would make up strings of digits which, when flipped over, spelled something. E.g. punch in 710.77345 and flip it over, it reads "ShELL OIL". 323375 spells "SLEEZE".
0 = letter "O"
1 = letter "I"
2 = letter "Z"
3 = letter "E"
4 = letter "h"
5 = letter "S"
7 = letter "L"
8 = letter "B"
6 and 9 don't make a letter. The challenge was to come up with words using only those 8 letters. Nowadays with all the available fonts there's an inverse for all 26 letters, though not all machines have all the fonts installed, as we've seen.