Answer based on context:

In their first season in the Midwest Division (NBA), Houston and the Kansas City Kings tied for second place with identical 40–42 records. The Rockets, with Malones 26.8 ppg and 14.5 rpg during the playoffs, reached the 1981 NBA Finals, but lost 4–2 to the Celtics. During the following season, Malone averaged 31.1 points with 14.7 rebounds and won his second MVP award. He repeated as the NBA leader in rebounds and was the runner-up for the leagues scoring title to George Gervin (32.3). He was also the league leader in offensive rebounds (558) and minutes played (3,398, 42.0 per game). At the end of the season, Malone earned his second placement on the All-NBA First Team. He set a career high in scoring average and also set a single-game career high with 53 points on February 2 against the San Diego Clippers. Nine days later, on February 11 against the Seattle SuperSonics, Malone eclipsed his own league record with 21 offensive rebounds. In Malones last season in Houston, the Rockets followed their NBA Finals appearance in 1981 with a first-round exit in the 1982 playoffs. Though he averaged 24.0 points with 17.0 rebounds, Seattle defeated Houston 2–1.

How many more rebounds did Malone average in the series than he did during the season?
.2