The 33-year-old won her 19th Grand Slam title when she beat Maria Sharapova to win in Melbourne.
Williams plans on cutting down on tournaments and focussing on winning, the Grand Slams starting in May with the French Open.
She told reporters: "When I think about Paris, I don't think about 20 (Grand Slams). I just think about winning there. It's the one Slam I don't have more than two titles. I only have two there. So I think now that I got this under my belt, I'm a little more comfortable with my ranking now. Now I can really move.
"I did so bad last year at Roland Garros, and Wimbledon as well (losing in the second and third round). So those are the two I really have my eye on, because I would like to do better at those. And I know I can do better. I'm not going into it as thinking of number 20, but I want to win Roland Garros.
"I definitely am not going to play as much this year and I'm just going to go for everything when I do play. But I'm not playing as much. (I) Try to be more focused in every tournament I get into."
Williams is now three Grand Slams behind Steffi Graf, who has won 22.