@Dave ***
as
@Tod ********
said its just like any other visa extension so you dont need to leave the country on the date originally stamped in your passport.
it is essentially resubmitting the same documents you used to apply for the dtv. however i was just letting people know you may need to provide a lot more proof of what you do to make your money if you're an online worker. in my original application, I was able to simply write in a cover letter what i did, give a web address and an instagram account. but to get the extension, that wasn't enough, they wanted more proof.