"To estimate these reductions" means to make an educated guess or calculation about how much something (usually quantity or value) will decrease or be reduced. Full definition
The non-profit research organization Resources for the Future estimates reductions in carbon could save 35,000 lives in the country each year by 2020. (wrvo.org)
Based on the weekly average ticket take of $ 10.5 million in fiscal 2014, the Citizens Budget Commission estimated the reduction could have bled about $ 10 million from city coffers. (nypost.com)