Measurement & attribution
Attribution
Attribution is the set of rules deciding which media touchpoints receive credit for a conversion. Every reported CPA and ROAS is a product of an attribution model - last-click, data-driven, platform-specific - so numbers from different models are different claims, not different results.
In practice
Platforms attribute generously to themselves; adding platform-reported conversions across channels routinely exceeds the conversions that actually happened.
Agree the source of truth and the model in the plan, and treat platform numbers as optimisation signals rather than the scoreboard.