When onboarding CRM data into AAM, please make sure you're viewing the traits cross-device graph / metrics. You can switch the view of the trait by selecting the drop down in the top right on the trait page.
With Cross Device ID, the volumes of population are coherent and similar to the ones in our CRM !
However, I took time to read the documentation you provided and I just can't get the difference between "cross-device ID" and "device ID" here since it is a CRM onboarding... Could you help me understand it ?
Also: the traits automatically populate segments associated to the onboarding, but why is the the segment population is different than the trait population ? I can't display by cross device ID here.