I was checking some old posts and i found something.
So here is it.
The Notation (or whatever it is)
Let define the alphabet.
Let assign numbers (in order) to the alphabet, starting with A = 1 and ending with Z = 25.
Let make a string of letters, each one inside a 
Let convert the letters into their assigned numbers.
Finally, let remove the 's and you should get a string of digits.
This is the result.
[A][X][A][Y] = 123124
[Z][L] = 2512
I have nothing to say.
Except that i wanted to do an extension, but couldn't figure out how to write it.