SNP - Manipulating the ATP Quantity

Hi,

I've been trying to reduce the ATP Quantity by the EG Category (DEP:CONRl ) orders at the source location so Distribution Demand (confirmed) orders reduce what is available(ATP). I've tried manipulating the ATP category groups AND tried different setting on the Scope of Check ( 'Incl.Rel.orders reqs' settings) but I don't seem to be affecting the change I require. Can anyone advise what I'm missing or point me at some info to help make this topic clearer.

Thanks

Andy