Existing SLED (&1) has been changed to &2 by the program

What causes this issue?

The system has calculated a shelf life expiration date (SLED) that is
different to the SLED entered in the item.

System Response

According to the system settings, this is a warning or an error
message.
If the message is a warning (W), the system allows the entry, but warns
you in case the entry was unintentional.
If you confirm the message, the system copies the new SLED it just
calculated to the item.
If the message is an error message (E), the entry is not allowed.

How to fix this error?

INCLUDE NA_EINGABE_PRUEFEN

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

If the message is an error message, cancel the activity that
recalculated the SLED (for example, changing the production date).
INCLUDE NA_MELDUNGSTYP_AENDERN

Error message extract from SAP system. Copyright SAP SE.