What are the functions of the A & B buttons?

Question: What are the functions of the A & B buttons?

In an unmodified DS-4000, the A button is the FOLDER button, used to select folders, and the B button is the PRIORITY button, used to insert a high-priority tag in an audio file being recorded. An Olympus Professional Dictation Products dealer can customize each of the buttons to perform the function of one of the following menu items instead of its default function:

• INDEX – Insert an Index Mark.
• FOLDER – Switch the folder into which your recording will be saved.
• DISPLAY – Toggle among seven formats of recording information, including date and time stamps, file length, remaining recording time, etc.
• REC MODE – Select the recording quality (SP or LP)
• MIC SENSE – Select the microphone sensitivity to CONF. or DICT.
• VCVA – Enable (ON) or disable (OFF) VCVA operation
• PRIORITY – Set the priority tag for the recording to HIGH or NORMAL
  Verification Source: Olympus Website