In an update to their website on January 22, 2025, U.S. Customs and Border Protection (CBP) published the latest version of their “E-Commerce Frequently Asked Questions” website.
This page already included clarifications on Section 321 and Entry Type 86 entries but it now includes information on Automated Commercial Environment (ACE) warning messages on the daily limit of $800 per person, per day is calculated and enforced.
The updated website can be found here:
https://www.cbp.gov/trade/basic-import-export/e-commerce/faqs