You need the ln prop ($sline().ln) which will return the line number, without it $sline() returns the text. $sline()


rline -l 1 @nickmatchs $sline(@nickmatchs,1).ln $sline(@nickmatchs,1) (Dropped)


Note also that commands in scripts do not need slashes.
Code:
  Drop all nicks:{
    msg nickserv fdrop $gettok($gettok($1,2,58),1,32)
    rline -l 1 @nickmatchs $sline(@nickmatchs,1).ln $sline(@nickmatchs,1) (Dropped)
  }