I learned to use QE by attending a workshop at an institute. However, the webpage for the course seems to be taken down. I will look for some materials and will update you.

@HemanthHaridas, I ran a vc-relax calculation of graphene and it gave me the correct result inside BURAI, as well as by using the python code provided by you on the log file. In both cases, the lattice constant converged to 2.46 Angstrom. So, I am pretty sure that there is something wrong with the youtube tutorial.

I think you might want to add your explanation (that you gave me in the comment) as an edit to your answer saying that the approach presented in the video is incorrect.

You can edit that. Thanks for letting me know that graphene worked fine