MANAGING IMPRESSION OPPORTUNITIES FOR A SET OF CONTENT ITEMS ASSOCIATED WITH GOALS TO GUARANTEE ACHIEVEMENT OF THE GOALS WITHIN A SPECIFIED PERIOD OF TIME

An online system guarantees achievement of an impression goal and a reach goal associated with a set of content items received from a content-providing user of the online system within a period of time associated with the goals. To ensure that the goals are achieved within the period of time, the online system may adjust values of filters associated with the set of content items that control a number of impression opportunities for which the set of content items will be eligible for presentation to users of the online system. The online system may compute a normalized ratio throughout the period of time associated with the goals based on the goals and the progress made by the online system towards achieving the goals. Based on the normalized ratio, the online system may track the performance of the content items and adjust the values of the filters.