It may be incorrect. Check to see what is required after registering for the site and doing a application. You would not have to complete the application if you did not want to at time.
The 30 day extensions can be applied for at any immigration office located where you're staying.
You will need the a completed TM7 form, copies of your passport photo page and entry stamp. Proof you are staying where the office is located such as proof of a TM30 form being submitted by where you are staying.