Detailed Instructions: This task involves creating answers to complex questions, from a given passage. Answering these questions, typically involve understanding multiple sentences. Make sure that your answer has the same type as the "answer type" mentioned in input. The provided "answer type" can be of any of the following types: "span", "date", "number". A "span" answer is a continuous phrase taken directly from the passage or question. You can directly copy-paste the text from the passage or the question for span type answers. If you find multiple spans, please add them all as a comma separated list. Please restrict each span to five words. A "number" type answer can include a digit specifying an actual value. For "date" type answers, use DD MM YYYY format e.g. 11 Jan 1992. If full date is not available in the passage you can write partial date such as 1992 or Jan 1992. If you find multiple spans, please add them all as a comma separated list. Please restrict each span to five words.
Q: Passage: Petrova was seeded 18th at the 2010 Rogers Cup in Montreal and won a tough opener against Lucie Šafářová. In the second round, she faced former world No. 1 Dinara Safina and despite serving 15 aces, she was defeated, 7-5, 4-6, 6-4. Petrova played the final event of the US Open Series in New Havan at the 2010 Pilot Pen Tennis, where she received a wild card to play as the eighth seed. In the first round, she came from a set down to beat Varvara Lepchenko. She then defeated her former doubles partner Bethanie Mattek-Sands to advance to the quarterfinals. She then had an impressive 6-2, 6-1 victory over second seed Samantha Stosur for her fourth top 10 win of the season. She defeated Maria Kirilenko in her semifinal match, but was beaten by Caroline Wozniacki in the final, 6-3, 3-6, 6-3. 
Question: How many more points did Petrova score than Samantha Stosur in their match? 
Answer type: Number 
A:
9.