Task: Question Understanding
Input (English): Passage: Sixteen international airlines provided regular flights to Khartoum. The number of domestic and international passengers increased from about 478,000 in 1982 to about 485,000 in 1984. Air freight increased from 6 million tons per kilometer in 1982 to 7.7 million tons per kilometer in 1984. As compared with the previous year, in 1989 passenger traffic on Sudan Airways fell by 32% to 363,181 people, reducing the load factor to 34.9%. By contrast, freight volume increased by 63.7% to 12,317 tons. At the end of 1979, Sudan Airways had entered into a pooling agreement with Britains Tradewinds Airways to furnish charter cargo service between that country and Khartoum under a subsidiary company, Sudan Air Cargo. A new cargo terminal was built at Khartoum.
Question: By how many millions of tons did air freight increase between 1982 and 1984?
Output (English): number