Post the following in the discards field exactly as I have typed it
(s/2)+1
where is 's' is the number of races and is replaced each time the
scoring series option is used with the number of races sailed so far.
If you hover the mouse over the filed you will see all he parameters
that you can use in a discard formula. If the information disappears
to quickly press the F2 key and a window will pop up with the same
information showing.