Asterisk 1.4: gui registration differs from non-gui

Hello, everyone.
I’d like to ask how does asterisk 1.4 with GUI register itself at the provider’s end (when I mark a checkbox ‘register’ while creating a “Service Provider”). Before I used to write something like:
register =>
in sip.conf. Having that line, asterisk would execute
exten => 924980111,1,…
when receiving the incomming call to 924980111. However, when I create a provider with the GUI and mark a checkbox ‘register’ that doesn’t happen. When I call 924980111 the extension ‘s’ is executed.
Please, could anyone write if it is possible to achieve the same behavior from gui.