Williams was unaware of her latest milestone when she stepped off court .
Her latest milestone took her beyond Chris Evert and one step closer to Martina Navratilova 's record of 306 matches won at majors .
Williams was unaware of her latest milestone , which took her beyond Chris Evert and one step closer to Martina Navratilova 's record of 306 matches won at majors , when she stepped off court .