As we go through the latest cut-off of 2020 then it shows that the closing rank for General category was 6278 for Textile Technology branch in IIT Delhi. See it is quite difficult to tell you about exact marks to score because for JEE-Advance no maximum marks are fixed but yes with regards to JEE-Advance 2021 if you secure your AIR in JEE-Advance under top 6200 then there are good chances for you to get IIT Delhi. For NITs and IIITs you have to score around 96 percentile or more in JEE-Main 2021.
You can check out the latest cut-offs from the link given below :-
Note that the above prediction is made on the basis of latest cut-offs available on official website of JOSAA and the cut-offs are bound to change every year depending upon various factors such as the number of candidates appearing in an examination, the number of candidates qualifying an examination, difficulty level of the paper, and so on.
To have a list of all those colleges which you can get based upon your JEE-Main score, category, and state you can use JEE-Main College Predictor :-
As you are preparing for JEE-Main or JEE-Advance 2021 the I would recommend you to check the resources made by our experts to help aspirants like you in the best and smart preparation of JEE-Main or JEE-Advance 2021 :-
I hope this information helps you.