Dual degree means 5 years. The cutoffs are lesser(still must get atleast 270+, 2017 was unique, dont go by that data). Directly, you wont get CS. You have to do one year that MSc course only. If your CGPA is good(almost everyone), then you will be offered to switch to BE degrees like EEE or Mechanical or ECE. If you work hard, you can achieve even CSE. Otherwise, if you are decent enough, Mechanical is a guarantee and even EEE.
To total you have to sudy one extra year and you will get 2 degrees.