Explanations / Notes:
For ID, a plain number (4) or number prefaced by G (G4) indicates an individual Game ID. A number prefaced by Gr (Gr4) indicates a Group ID. A number prefaced by S (S4) indicates a Super Group ID.
Abbreviations are necessary because pulling a full game title from the database would be much too big for the legend, and any sort of automated abbreviation generator would result in much goofiness.
The Sum From Date is for counting a game's sales from a certain point. It will look for the most recent lifetime total BEFORE the date you give, then subtract that from all subsequent totals to determine how much it has sold since. Of course, if you pick a week that's 4 weeks since the last known total and 10 weeks before a new number, it's not going to have a number for exactly the time you wanted.