SKAdNetwork (SKAN) sends delayed, aggregated postbacks to the ad network that drove an install. Advertisers encode post-install behaviour into a limited conversion value. SKAN 4 introduced multiple postbacks over different windows, fine and coarse conversion values, and privacy thresholds that reduce detail for small campaigns.
Designing the conversion-value schema — which revenue ranges and events map to which values — is one of the highest-leverage measurement decisions on iOS.