As you have mentioned that you joined I have joined BTech in 2015, You total years will be in continuity i.e a total of 8 years from the year you joined B.Tech (2015 - 2023). The gap or detained or drop in the middle is due to your backlog that you were not able to clear within the prescribed time allotted by the university.
You need to understand your university rules which allow a certain amount of backlog that you can carry forward to the next semester/year but need to clear within the next year or else you will not be promoted to next year. Once you clear that subjects or the total no. of subjects that are allowed by the university to carry forward, you can continue in the next semester/year.
The Engineering college/university allows 8 ATKT's in total (5 External and 3 Internal i.e. viva, practicals, Unit Test) as per new rules and also you will have to clear all your 1st year ATKT's before the completion of 2nd year i.e while giving your 4th-semester exam or else you will get a drop. Also, note that even though you clear your previous year backlog but have exceeded the total number of ATKT's that you are bound(8 nos) to, you may get a year gap and the rules follow for all semester/years. So as per university rules, one gets a chance to clear his/her backlogs or ATKTs (1st sem backlog to be cleared in the next 3 chances 2nd, 3rd and 4th semesters & 2nd sem backlog to be cleared in your 3rd and 4th semesters).
“The most important thing in life is to learn how to give out love, and to let it come in." — Morrie Schwartz