Please answer the given financial question based on the context.
Context: supplementary information on oil and gas producing activities ( unaudited ) c o n t i n u e d summary of changes in standardized measure of discounted future net cash flows relating to proved oil and gas reserves ( in millions ) 2006 2005 2004 sales and transfers of oil and gas produced , net of production , transportation and administrative costs $ ( 5312 ) $ ( 3754 ) $ ( 2689 ) net changes in prices and production , transportation and administrative costs related to future production ( 1342 ) 6648 771 .
|( in millions )|2006|2005|2004|
|sales and transfers of oil and gas produced net of production transportation and administrative costs|$ -5312 ( 5312 )|$ -3754 ( 3754 )|$ -2689 ( 2689 )|
|net changes in prices and production transportation and administrative costs related to future production|-1342 ( 1342 )|6648|771|
|extensions discoveries and improved recovery less related costs|1290|700|1349|
|development costs incurred during the period|1251|1030|609|
|changes in estimated future development costs|-527 ( 527 )|-552 ( 552 )|-628 ( 628 )|
|revisions of previous quantity estimates|1319|820|948|
|net changes in purchases and sales of minerals in place|30|4557|33|
|accretion of discount|1882|1124|757|
|net change in income taxes|-660 ( 660 )|-6694 ( 6694 )|-627 ( 627 )|
|timing and other|-14 ( 14 )|307|97|
|net change for the year|-2083 ( 2083 )|4186|620|
|beginning of year|10601|6415|5795|
|end of year|$ 8518|$ 10601|$ 6415|
|net change for the year from discontinued operations|$ -216 ( 216 )|$ 162|$ -152 ( 152 )|
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Question: what was the average upward revisions of cash flow of previous quantity estimates during the three year period , in millions?
Answer:
1029.0