Updates documentation for the new config variable

Author: tuupke

doc/manual/running.rst

@@ -106,9 +106,12 @@ show for submissions after the freeze. It is possible that new
 entries appear for some times after the freeze, if the result of
 a submission before the freeze is only known after (this can also
 happen in case of a :ref:`rejudging`).
-The global configuration option ``show_balloons_postfreeze`` will
+The global configuration option ``minimum_number_of_balloons`` will
 ignore a contest freeze for purposes of balloons and new correct
-submissions will trigger a balloon entry in the table.
+submissions will trigger a balloon entry in the table. This only
+happens when the team problem has not received the amount of balloons
+set by the configuration option and the newly solved problem must have
+been solved before the freeze. This is to prevent an information leak.
 
 Static scoreboard
 -----------------