When campaigns are created using targeting permutations, each targeting permutation results in an adset which requires a share of the overall campaign budget. It is important to note that Facebook imposes a rule that every adset should get a minimum budget of at least twice the bid amount.
StitcherAds offers 2 types of budget distribution to choose from; Even and Weighted.
Even Distribution (Link Clicks, Impressions)
Taking into consideration Facebook's rule that every adset should get a minimum budget of at least twice the bid amount, StitcherAds allocates the required budget to each adset first and then distributes the remainder of the overall campaign budget evenly across all adsets.
Weighted Distribution (Link Clicks, Impressions)
StitcherAds weighted budget distribution honours Facebook's "budget-must-be-twice-the-bid" rule by allocating the minimum budget necessary for each adset. The remaining budget is allocated proportionally based on the reach estimate for the adset.
Targeting permutations result in variant audience sizes per adset within a campaign. With Weighted Distribution the campaign budget is split more logically based on the potential reach of those adsets.
Even & Weighted Distribution for Conversions bidding (oCPM)
The "budget-must-be-twice-the-bid" rule does not apply to conversion bidding (oCPM) bid types.
Discrepancy in the totals
Because of the calculations involved and the necessary rounding of divided budgets, you may see a small discrepancy of up to 0.05 between the sum total of your adset budgets and the specified campaign budget. The total of the adset budgets will, however, not exceed your stated campaign budget.