The Overview is an executive summary of all your optimizations, with a period selector for 7, 14, or 30 days. It shows total Spend, blended MER (overall return on spend, calculated with real sales when you have a sales integration connected, or with pixel ROAS when you don't), Results with the average CPA, and how many optimizations are healthy out of the total active. Below the numbers, it highlights the Top performer and the Worst performer among your optimizations, with ROAS, spend, and results for each. Highlights only appear when an optimization has spend above US$50 in the period. Below that, there isn't enough data.