“8.2.14 LET - and STO - Variables
One can define variables to be used in the following records. After the leadin LET# (only valid within current program) or STO# (value will be saved to database) the name of the variable is appended directly (up to 16 characters of an alpha-numerical text, 1st character has to be a letter) and an optional index.”
The first 16 characters of your variables are NOT significant