FBI agents broke seals for classified materials in POTUS's possession.
Docs are literally sealed.
ONCE POTUS was briefed, official copies were made appropriate for storage.
They opened the seals that have the docs inside.
https://www.gsa.gov/buy-through-us/purchasing-programs/requisition-programs/gsa-global-supply/national-stock-numbers/security-containers
https://cmls.gsa.gov/s/publication-details/a12t0000004sEuNAAU/ca0026824?language=en_US