iProcurement error

Dears,

if anyone helps me on this error, recently i setup the internal requisition starts from iProcument and end on sales order,

but i face this issue when i try to make an intrnal requisition from iProcurment and no quantity available on destination inventory i got this error "You cannot proceed with Internal Requisition as there is no stocks available", i receipt quantity in the source inventory and try to make Internal req. from it to the destination, is i'm right??

why the system checks the qty on the destination inventory ? and from where i tell the system this is source inv. and this is destination inv. i do that on shipping network