This all has to do with how the web UI works, and the entire design. Note that you CAN change the “tab order” but it is not by changing numbers… it is literally by changing teh position on the screen. The browser goes through the fields in the sequence they appear on the screen, but there is also the concept of grouping fields, and so once grouped, it will also follow the sequence of those groups as well. so by regrouping and rearranging fields on the screen, you can define an order for the fields that works for you.