India were 27 for two in their chase when bad light brought an end to the day, with South Africa needing eight wickets for victory and a 2-0 series win on Wednesday.
But the visitors showed little urgency in setting their total and whether they have left themselves enough time to get the win, and vital World Test Championship points, remains to be seen.
"We obviously looked at how best we were going to use the new ball, because in the morning we still wanted a newish, hard-ish ball," Conrad told reporters.
"What we felt is that when the shadows come across the wicket in the evening, there's something in it for the quick bowlers, so we didn't want to declare too early and not be able to use that.
"And then, obviously, we wanted the Indians to spend as much time on their feet out in the field, we wanted them to really grovel, to steal a phrase, bat them completely out the game, and then say to them 'Come and survive on the last day and an hour this evening.'
“So, so far so good, but we also know that they're not just going to roll over, we're going to have to be at our very best in the morning.”
Conrad says time will tell if their decision to hold off on a declaration, or not build such a lead sooner, will be costly.
"I don't think there's a right and a wrong in anything. We wanted India to come out again after lunch and spend time on their feet,” he said.
“We saw the effects of batting for two full days in the first innings and what sort of effect it had on them. And it was never going to be easy for the opening batters to come this evening, with the new ball and shadows across the wicket.
“We felt we could have struck there. If tomorrow evening comes and we have them eight down and people say, 'Well, see you told you so'… we've got to base it on our sound judgement and if that doesn't work out, it doesn't.
“I don't think there's a right and wrong in any of this but obviously, 2-0 (series win) is a lot better than 1-0. I'd like to think that the series is secured and we're going to go all out for the win."
South Africa won the first test in Kolkata by 30 runs.