The firmware internally still stores the number of expansion boards. However, since that assumes each expansion board is 8 stations and our current expansion board (2.0) has 16 stations, in the past it has always created confusions to users exactly how many expansion boards they should set. Therefore we decided that the UI should show the number of stations to avoid confusion.
The controller can automatically detect the number of expansion boards (so when you plug in expansion boards the UI should show you the available number of stations). In practice, because some users may want to enable virtual (e.g. RF) stations, we still leave this option as a user-settable option.