They pretty much put the whole keyboard in there !
Spoiler
48 characters, try making pairs first
zl ss sf ;d ar pb /k pp zi qb /, qm pp al /k zf zc w/ q, pk xv zd ;k /a
See how the pairs start with mostly the same characters? z s ; a p / q… Looking at your keyboard (QWERTY-US) see how they are under the numbers 1, 2 and 0? Lets get the keyboard column for each of the characters
zl ss sf ;d ar pb /k pp zi qb /, qm pp al /k zf zc w/ q, pk xv zd ;k /a
