NEW YORK — Maybe Serena Williams simply wanted to put on a better show for her pal Beyonce.

Looking rather displeased with herself at times, including when she shook her head and smirked on the way to the net for a post-victory handshake Thursday night, Williams still managed to tie Martina Navratilova’s professional-era women’s record with her 306th career victory in Grand Slam matches.

Williams beat Vania King 6-3, 6-3 to reach the U.S. Open’s third round.

“I just think it should have been a different scoreline for me. I feel like I made a lot of errors,” Williams said. “But, you know, there’s nothing I can do about that now. What really matters is I got the win. Hopefully I’ll just get better.”

Really? This performance didn’t seem OK? After all, Williams delivered 13 aces with serves that reached 121 mph. She compiled a 38-4 edge in winners. She only dropped six games and needed all of 65 minutes to win.

“I just didn’t have a great day,” was her assessment.

Yes, there were problems. The 28 unforced errors The return game: She won only 13 of 40 points on King’s first serves. Williams did, however, smack one backhand return winner in the final game.

Music power couple Beyonce and Jay Z sat behind Williams’ coach, Patrick Mouratoglou, in the player’s guest box Thursday.

“It’s always good,” Williams said casually, “to have Beyonce and Jay in the box.”

King noticed Williams’ negative body language as she headed to the net.

“I think Serena’s a perfectionist. She always wants to play her best. … If she doesn’t play really well, she’s always a little bit hard on herself,” King said.

Delivering 13 aces with the roof closed at Arthur Ashe Stadium, and showing no signs of a sore right shoulder that she said requires “constant” treatment, Williams improved to 306-42 in matches at major tournaments. Navratilova retired with a 306-49 mark.

Only Roger Federer, with 307, has won more Grand Slam matches than Williams in the Open era, which dates to 1968 – and he won’t add to that total during this tournament because he is out for the season as he rehabs his surgically repaired left knee. Williams can equal Federer’s total by beating Johanna Larsson of Sweden on Saturday.

Earlier, Williams’ older sister, seven-time major champion Venus, beat Julia Goerges 6-2, 6-3, while No. 5 Simona Halep eliminated Lucie Safarova 6-3, 6-4.

In men’s action, Andy Murray defeated Marcel Granollers 6-4, 6-1, 6-4. Also advancing were 2009 champion Juan Martin del Potro, No. 3 Stan Wawrinka, No. 6 Kei Nishikori, No. 8 Dominic Thiem, No. 14 Nick Kyrgios and No. 22 Grigor Dimitrov, but No. 16 Feliciano Lopez lost to Joao Sousa 6-2, 6-4, 1-6, 7-5.