Hello Shivam
Traffic is considered inbound or outbound depending on where the physical location of the actual prefix is. Remember, that a prefix, or a subnet, is connected to a particular router interface. That router will place that prefix within its routing table as a directly connected network, and will share the prefix with other routers running the same routing protocol. In order for other routers to reach that prefix, they will run their routing algorithm and determine the outgoing interface from which all packets destined for that particular prefix should exit from.
So to answer your question, whether traffic is incoming or outgoing depends upon the topology, the physical location of the prefix/subnet, the location of the sender within that topology, and the perspective (the point of view of which router) you are looking at the topology from.
I hope this has been helpful!
Laz