The medications described are Schedule II, which is defined as "The drug or other substance has a currently accepted medical use in treatment in the United States or a currently accepted medical use with severe restrictions."
One citation for the limits being secret are:
Ike Swetlitz, I (2023) "Xanax and Adderall Access Is Being Blocked by Secret Drug Limits". Bloomberg, Online edition. https://www.bloomberg.com/news/articles/2023-04-03/adderall-...
> Xanax and Adderall Access Is Being Blocked by Secret Drug Limits
> The Drug Enforcement Administration regulates the manufacturing, distribution and sale of controlled substances, which can be dangerous when used improperly
> the limits themselves are secret.
> A Cardinal Health document reviewed by Bloomberg News says that limits are calculated on a daily, monthly, and quarterly basis.