Unit &1 is treated like the unit Piece (ISO Code PCE)

What causes this issue?

You are checking whether the number of geometric instances under an item
variant matches the quantity specified in the item variant. The system
determines that the unit of measure specified in the item variant is
dimensionless but is not a "piece" unit with ISO code "PCE".

System Response

The system displays a warning and treats the quantity specified in the
item variant as if it relates to the unit "piece" (ISO code "PCE").

How to fix this error?

If the unit of measure specified in the item variant can be considered
identical to the unit "piece" (ISO code "PCE"), you can ignore the
warning. Otherwise, you have to specify a quantity in the item variant
with respect to a unit with ISO code "PSE", so that the consistency
check can produce meaningful results.

Procedure for System Administrators

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

Error message extract from SAP system. Copyright SAP SE.