I get this error cant understand

[Smartman_xd]

my skript

options:
    deny-username-message: &8> &4You can't put your username here&8!
    no-referral-message: &8> &4Ok&8! &4A person didn't tell you about the server&8.
    thank-you-message-1: &8> &aThank you for telling us &2%player%&8!
    thank-you-message-2: &8> &aThank you for inviting &2%player% &ato the server&8! &aYou earn 1 refer token!
    already-answered: &8> &4You already answered this&8!
    referral-1: &8> &aWho told you about the server? Please type /referral (username of who invited you)&8!
    referral-2: &8> &cType /referral none&8, &cif nobody invited you&8.

on first join:
    set {referral.%player%} to true
    wait 5 seconds
    message "{@referral-1}"
    message "{@referral-2}"

command /referral <offline player>:
    trigger:
        if {referral.%player%} is true:
            if arg 1 is player:
                message "{@deny-username-message}"
                stop
            if arg 1 is "none":
                message "{@no-referral-message}"
                set {referral.%player%} to false
                stop
            else:
                message "{@thank-you-message-1}"
                add 1 {refertoken.%arg 1%}
                if arg 1 is online:
                    message "{@thank-you-message-2}" to arg 1
                    set {referral.%player%} to false
        if {referral.%player%} is false:
            message "{@already-answered}"
            stop

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

 

[HI46]

add 1 to {refertoken.%arg-1%}