my skript

Code (Text):

1. options:
2.     deny-username-message: &8> &4You can't put your username here&8!
3.     no-referral-message: &8> &4Ok&8! &4A person didn't tell you about the server&8.
4.     thank-you-message-1: &8> &aThank you for telling us &2%player%&8!
5.     thank-you-message-2: &8> &aThank you for inviting &2%player% &ato the server&8! &aYou earn 1 refer token!
6.     already-answered: &8> &4You already answered this&8!
7.     referral-1: &8> &aWho told you about the server? Please type /referral (username of who invited you)&8!
8.     referral-2: &8> &cType /referral none&8, &cif nobody invited you&8.
9.  
10. on first join:
11.     set {referral.%player%} to true
12.     wait 5 seconds
13.     message "{@referral-1}"
14.     message "{@referral-2}"
15.  
16. command /referral <offline player>:
17.     trigger:
18.         if {referral.%player%} is true:
19.             if arg 1 is player:
20.                 message "{@deny-username-message}"
21.                 stop
22.             if arg 1 is "none":
23.                 message "{@no-referral-message}"
24.                 set {referral.%player%} to false
25.                 stop
26.             else:
27.                 message "{@thank-you-message-1}"
28.                 add 1 {refertoken.%arg 1%}
29.                 if arg 1 is online:
30.                     message "{@thank-you-message-2}" to arg 1
31.                     set {referral.%player%} to false
32.         if {referral.%player%} is false:
33.             message "{@already-answered}"
34.             stop
35.  
36.                                                  

Error: Cant understand this condition/effect: add 1 {refertoken.%arg-1%} (refer.sk, line 28: add 1 {refertoken.%arg 1%})