In your "UPDATE" page (https://sqlite.org/lang_update.html), at the section of "2.2 UPDATE FROM", there is this "GROUP BY 2)" in the example:

 UPDATE inventory
   SET quantity = quantity - daily.amt
  FROM (SELECT sum(quantity) AS amt, itemId FROM sales GROUP BY 2) AS daily
 WHERE inventory.itemId = daily.itemId;

Is this "2)" should be "itemId"? Or maybe it is some sort of syntax I don't understand?

It also appears in the other two examples in 2.2.1.