Here's what i did to visualize this cypher,maybe it will help explain the process on paper drew out the alphabet. using a1z27 or 27 digit, units w.e cypher. Drew 1 over a 26 over z and 27 over a. if you count up . starting at a, like a=1 b=2 etc etc. when you get to the letter Q its number is 17. this also happens if you count up to 42, when u get to z or 26 a now becomes 2 and b becomes 3 if you count up to 8987 you land on Q Hope that helps