you should use /var as opposed to /set so there is no need to unset %calc*
you could save yourself a lot of lines if you use an alias to calc %calc2-4 instead

on *:TEXT:!csa*:#:{
  if ($2 == Flaming) { noop $csa($calc(( $3 *5*12000)*1.333),$nick) }
  elseif ($2 == Ballistas) { noop $csa($calc(( $3 *5*12000)*1.667),$nick) }
}
alias csa {
  var %calc = $1,%calc2 = $bytes($calc( %calc * 1.5),b),%calc3 = $bytes($calc( %calc * 1.3),b),%calc4 = $bytes( %calc,b)
  .notice $2 Your Sa with Other is: %calc4
  .notice $2 Your Sa with Orcs is: %calc2
  .notice $2 Your Sa with Undead is: %calc3
}

is an example it shouldn't be that hard to add the rest