The sum selection works like this;

• put the cursor in the "Enter a 6/49 sum" box and click
• a flashing cursor will appear in the box
• pick a number between 21 an 279.
• enter that number in the "6/49 sum" box
• click on the select button
• a window will appear, select "OK"
• the selection ( 6 numbers ) will appear in the "Selection" box
  (note: do not put any numbers in the "Selection" box)
• enter new sum numbers in the "6/49 sum" box or
  continue to hit the select button for more combinations