Mr. Brown is correct. In practical terms, what this means is that Kodak's recommended times are for one roll of 35mm or 120 film in 100ml (8 oz.) of undiluted stock. So if you dilute the stock 1:1 you should still use it to develop only one roll. That means using 16 oz. of diluted developer for one roll of film.(posted 8992 days ago)Given that you can fit two rolls of 35mm film into a 16 oz. tank, you may want a more efficient option. Here it is: when developing more than one roll of 35mm/120 film in a 1:1 dilution, increase your developing time by 15%. This is what Kodak recommends in their tech sheet for Xtol, albeit in very small print. If you dilute at 1:2, add another 15%, and add yet another 15% for 1:3.
BTW, even though one roll of 220 film will fit into a 16 oz. tank of developer, it still counts as two rolls because of its increased surface area. Adjust your times accordingly.