More than & materials selected, please limit your selection

What causes this issue?

You are attempting to make a mass selection of more than 1000
materials. This would cause you problems with system performance. There
is currently no option available for branching to a more detailed
material selection screen here, prior to passing your selection on to
module functions.
The maximum number of 1000 for this function has been defined as the
SAP standard value on the basis of experience.
You can only increase this number by means of a modification (ABAP
include MWWCONST - counter MAX_Z_AV_...). If you take this route,
however, SAP can no longer guarantee a high level of system
performance.

System Response

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

How to fix this error?

Use different selection criteria or enter the individual material
numbers manually in the module items.

Error message extract from SAP system. Copyright SAP SE.