Hello Omkar.
There's an option at the time of filling the form regarding the appearance in Improvement exams. You need to check that, for a yes.
Then, at the time of document verification, if you have the marksheets from the improvement exam, it is considered, otherwise you will have to submit the marksheets of the originally appeared exam and those marks are considered.

And as far as I know, the results of HSC improvement might not be announced by the time you take admission into college.