What are the meanings of these codes?

JJD - "I/P Subassembly Not Installed (Modular Optimization Method Only)"

JL4 - One source says "Stabilitrak" while another says "Control - Active Brake"

MX0 - "Merchandised Trans - Automatic Provisions, O/D"

R6F - "IDENTIFY B CODE USERS"

R9N - "PROCESSING CODE - SEAT"

VVI - Unknown

YT1 - Unknown

1SZ - " SUN AND FUN EDITION PACKAGE DISCOUNT "

I couldn't find any information about the VVI and YT1 codes. Does anyone have any idea what they're for?