The default letter sequence is “ABC…abc…” All 26 letters of the alphabet are used. The start letter “A” is assigned to the first 30 minutes starting at the session time range start time.
A custom letter sequence can be entered in Custom Letter Sequence
below the option above. Any character on the keyboard can be used.
To customize the start letter of the sequence (the letter assigned to the first interval beginning at the session start time), enter a value for the Start Letter
option right below the Custom Letter Sequence option.
Properties -> Profile (Tab) -> Use Custom Letter Seq. -> checkbox