ADSL2 ( Assymetrical Digital Subscriber Line 2 ) is a standard for delivering internet connectivity through telephone connections. It is designed to work approximately twice as quickly as ADSL. which means speeds of up to 24Mb/s for downloads and 3.5Mb/s for uploads are theoretically possible.
It has no effect on the amount of bandwidth is used and in most cases if your internet provider has a cap in place of 5GB. per month then that would mean 5GB. of data sent using ADSL2 (the overhead for the method of transmission is usually not counted as part of the usage cap.)