Inbound and Outbound can be deceiving. You have to look at it as 'in or out' of the physical port. For instance, traffic flowing from inside your firewall to outside would generally be considered outbound traffic. But technically this really is inbound to the inside interface and outbound from the outside interface. So to write an acl for this traffic you would have two options. An access list applied into the inside interface or out of the outside interface. Hope that helps a little.
