This is relative probability compared to the rest of the loot items on the table. A 10 here and another item with a 10 probability would give equal chance to both items.
Quantity
Always include this item in the results, overriding the probability. This will override the inner_table.
Only ever include one of these in the results. Ignores items from the inner table.
If this item is rolled, instead roll on the selected table. This is overridden by the Always option.