It simply spells out the order of command that asterisk will execute. So you 1 just means it will be exucuted first. You could have it answer then play message (please wait when we try to reach ) and then dial extension so in that case we would have exten => 500,3,Dial(SIP/magne)
It means you haven’t done your basic reading, in this case page 123 of Asterisk: The Future of Telephony, which is available online via asteriskdocs.org/