Opener Jaffer, who had scored a total of 67 runs in his four previous innings in the series, made 116 in India's 254 for three on day one.
"I have not scored enough runs on the tour, and I am really thankful that management have stuck by me and given me the chance to play this kind of innings because I was definitely under pressure," Jaffer told a news conference.
Jaffer said the flat and dusty pitch, unlike the usual fast and bouncy South African surfaces, suited the Indian batsmen.
"It's already spinning, and there are already footmarks on it. It looks like an Indian wicket," he said. "When we saw it the day before the game we were a bit surprised to have a wicket like that in South Africa."
Jaffer said he had formed a sound understanding with Dinesh Karthik, who scored 63, despite the fact they opened the batting together for the first time.
"We are pretty good friends, we have sat next to each other on the bus for the whole tour so I know him as a person," Jaffer said.
South African coach Mickey Arthur was satisfied with his team's performance.
"I think we bowled fairly decently as a unit," Arthur said. "India haven't got away from us, we still have a new ball in our hand, and if we can strike early tomorrow we'll be happy."
Arthur also expressed his surprise at the pitch.
"It certainly wasn't what we were looking for, but you've got to play well on what you're given," he said.
Arthur compared the pitch to the one prepared for a drawn Test against New Zealand in Cape Town in April, which yielded a double century and two other centuries.
"The wicket we had here against New Zealand last year looked pretty similar, but it didn't really deteriorate over five days," Arthur added.
Jaffer said India would look to total 450 to 500 but Arthur hoped for less.
"If we can restrict them to 380 we'll be happy, but then we're going to have to bat very well," he said. "We're still going all out for the win, we're not going to hang around just for a draw."
The series is level at 1-1.
