With Nielsen overnight averages for the World Series finale significantly lower than last year’s, the national box office leaders over the weekend showed a 25% increase from the comparable 1991 frame. The top 10 total rose to $ 36,736 ,075 from $ 29,468,087, but was down 12% from the previous weekend’s $ 41,832, 581.The B.O. benefited because the concluding sixth game of the Toronto-Atlanta World Series Saturday night was no ratings match for the finale of the all-U.S. 1991 series between Minnesota and Atlanta (national ratings will be released today). The 1991 series stretched to a seventh game, cutting into both Saturday and Sunday B.O. As reported yesterday, Warner Bros.’ action smash “Under Siege” dominated the B.O. for the third straight weekend, collecting $ 9,024,560, down just 19%. New pix in the top 10 included WB’s sixth-place C&W yarn “Pure Country,” doing good biz in the South and Southwest but not much elsewhere, and Universal’s seventh-place comedy/horror entry “Dr. Giggles,” scaring up little cash. In limited breaks, Triumph’s interracial romance “Zebrahead” didn’t show much in the way of B.O. stripes; Miramax’ crime tale “Reservoir Dogs” bared some teeth; RKO’s sperm-bank comedy “Frozen Assets” looked frigid; and Triton’s B&W comedy “In the Soup” stirred up OK numbers. WB had stylish results from the reissue of Sergio Leone’s 1984 gangster epic “Once Upon a Time in America” in the director’s cut (227 minutes) in one L.A. joint. But WB’s documentary “The Magical World of Chuck Jones” sketched lightly on a single L.A. easel. Front-runner “Under Siege” averaged $ 4,014 on 2,248 decks during its socko third attack. The 17-day take is a brawny $ 42,581,109 for the Steven Seagal pic ,which was closing in fast on the action star’s personal-best B.O. mark of $ 44 million (for Fox’ 1990 “Marked for Death”). Fox’s oater “The Last of the Mohicans” remained in second during its fifth battle, declining a moderate 24% to a chipper $ 4,450,251, or $ 2,412 per in 1, 845 canoes (splashing out of seven). The 31-day B.O. is a valiant $ 49,808,895. TriStar’s “Candyman” showed unusual second-weekend strength for a horror pic, declining a mere 22% to a sweet $ 4,220,850 as it climbed from fourth to third on the chart. With $ 2,850 per in 1,481 stores (entering 230), it advanced its 10-day total to $ 11,176,410. Buena Vista’s peewee hockey comedy “The Mighty Ducks” remained ducky in its fourth twirl with a 23% falloff to a cheerful $ 4,203,206 as it traded places with “Candyman.”"Ducks” averaged $ 2,271 in 1,851 rinks (leaving six), pushing the Disney pic’s 24-day take to a quacking $ 26,737,738. BV’s psychological thriller “Consenting Adults” (Hollywood Pictures) had an acceptable 26% decline in its fair second frame to $ 3,703,579, or $ 2,408 per in 1,538 beds (entering 25). The 10-day take is a not-so-spicy $ 10,287,053. “Pure Country,” a vehicle for C&W star George Strait, collected a moderate $ 2,739,680 in its opening gig in 993 arenas ($ 2,759 per). In the South and Southwest, which accounted for 415 of those sites, the pic averaged a nifty $ 5, 200, counterbalancing its weakness elsewhere. “Dr. Giggles,” starring Larry Drake as a demented surgeon wannabe, chopped up only $ 1,615 per in 1,681 operating rooms during its $ 2,714,815 initial slicing. Fox went wide with “Night and the City,” nabbing eighth place with the Robert De Niro-Jessica Lange crime drama, but it averaged a quiet $ 2,324 while going from one to 1,100 canvases, takingin $ 2,556,830. The 10-day take is $ 2,624,861 . Columbia had terrif results as it broadened Robert Redford’s “A River Runs Through It” from 24 to 130 hatcheries. Averaging $ 12,203, “River” reeled in $ 1 ,586,359 to take ninth, running its 17-day total to $ 2,643,407. The pic widens to more than 700 rapids this weekend. “Zebrahead” brought in a placid $ 2,426 per in 251 spots during its $ 609,000 16th-place debut. “Reservoir Dogs” averaged an OK $ 7,781 in 19 showcases during its $ 147,839 opening. “Frozen Assets” deposited $ 1,204 per in 103 banks during its $ 123,979 arrival. “In the Soup” cooked up a not so chunky $ 6,961 per in two Gotham tureens during its $ 13,922 start. “Once Upon a Time in America” scored a healthy $ 5,186 as the lengthy opus arrived in its single L.A. safehouse. “The Magical World of Chuck Jones,” a look at the life and work of the celebrated WB cartoon creator, saw $ 2,900 in one L.A. site.