Why do impressions not match between AA and Microsoft Advertising?

[PeterWoodroffe]

We've recently implemented advertising analytics. Our AMO impressions, clicks and spend data matches the google ads platform. However, for Microsoft ads our impression figures are 16% lower in AA than Microsoft ads. Our Clicks and spend data is 1.8% lower.

On a campaign basis we've identified that the variance is mainly from dynamic search ads. Are there any set up variances required to correctly capture DSA data in AA?

Thanks