Hi AA,
The warning message S_V8 is applicable for ATP relevant interchangeability groups. It means that the product or product combination of this group are already there in other ATP relevant interchangeability groups.
To avoid this, make sure product does not exist in multiple groups or if you do not want system to carry out this check you can make this as active or inactive in customizing under Master data>Product and Location interchangeability>Consistency checks>Maintain validation.
Regards,
Umesh