[Kanegasi]

I'm assuming you're talking about the new countdown feature on the alpha. Unfortunately, the /countdown command does not parse any secure macro options and only accepts numbers. However, you can skip the command and go straight to the function.

/run if SecureCmdOptionParse("[btn:2]") then C_PartyInfo.DoCountdown(3) else C_PartyInfo.DoCountdown(10) end

Here's the command implementation if anyone's curious:

SlashCmdList["COUNTDOWN"] = function(msg)
    local num1 = gsub(msg, "(%s*)(%d+)", "%2");
    if(num1 ~= "" and tonumber(num1) <= MAX_COUNTDOWN_SECONDS) then
        C_PartyInfo.DoCountdown(num1);
    end
end

MAX_COUNTDOWN_SECONDS is currently 3600 seconds, or one hour.