On what is historically the slowest weekend at the box office -- the weekend after the Labor Day holiday, ticket sales were ... not bad, especially for the Vin Diesel sci-fi sequel Riddick, which managed to rake in $19.03 million. That was about twice what any other film earned at the box office last year -- and, for that matter, this year as well. With the top 12 films at box office earning $66 million versus $52 million for the top 12 a year ago, Riddick was single-handedly responsible for about 75 percent of the growth. The Spanish-language Instructions Not Included also helped lift the box office as it expanded to 717 theaters where it grossed $8.15 million, producing the best per-theater average of any film in wide release. After 10 days, it has already grossed $20.4 million. On the other hand, theaters showing One Direction: This Is Us were largely empty during its second weekend as sales plummeted a whopping 74 percent to just $4.05 million for the 3D concert documentary.