KL Rahul and Agarwal started the Indian innings well. But before the end of the first day, India ended their innings with just 202 runs. They needed to collect at least 300 runs if they wanted to fight to win the match. South Africa scored 35 runs and lost Markram's wicket. With a little bit of patience from the batsmen, it will not be a difficult task to give a good run lead by overcoming the mark of 202 runs. I would expect South Africa to be ahead by at least 100 runs.
India could have easily scored 100 more runs. Rahane and Pujara both had a disappointing inning. If Rahul could make his innings longer, it would've been quite nice.
But with the batting order, South Africa have, I think they will be able to manage a healthy lead but also India to have the bowling lineup to destroy any batting lineup within a blink of an eye.