"Attempt to call number" error when dealing with variables.

I currently have an XP turtle set up to collect experience, then enchant the books. I'm attempting to make him display a line, similar to the following:

Enchanted # books so far, and currently level #.

Here is my full code:

level = 0
local num = 0
num = 0
xp = peripheral.wrap("right")
xp.setAutoCollect(true)
while true do

-- Detect if it's level 30 and enchant
if xp.getLevels() > 30 then
  turtle.select(1)
  turtle.suckUp()
  drop = turtle.getItemCount(1) - 1
  turtle.dropUp( drop )
  xp.enchant(30)
  num = num + 1

-- Store the enchanted book
  turtle.drop()
  sleep(5)
end

-- Display
level = xp.getLevels()
term.setCursorPos(1, 1)
term.clear()
print("Enchanted " ..num "books so far, and currently level " ..level)
end

When the script runs, even without the additional level displaying (just print("Enchanted" ..num)), it returns an error saying the following:

27: attempt to call a number

In the lua prompt, I can run

print ( num )

and it will return the correct number. But I can't seem to use it with any sort of text. Any assistance would be apprecieated.

Split into new topic.

You need the concatenation operator on both sides of the variable, not just one.