There\'s always little sill things you could do to shorten the script. I\'d review it and see if it works, but it seems you need 2 people to play, and nobody else is on right now ;P

  if (%numgame == 1) { msg $chan 12Game already in progress. }
  if (%numgame != 1) {

can simply be

if (%numgame == 1) { msg $chan 12Game already in progress. | HALT }

and

     if (%currentnum < %end) { msg $chan 12The number is now4 %currentnum }
    if (%currentnum >= %end) {

could simply be

if (%currentnum < %end) { msg $chan 12The number is now4 %currentnum | HALT }