The description (in management model AND the XSD file!) for max-outbound-messages is

The maximum number of outbound channels to support for a connection.

and for max-inbound-messages

The maximum number of inbound channels to support for a connection.

for max-outbound-channels:

The maximum number of concurrent outbound messages on a channel.

for max-inbound-channels:

The maximum number of concurrent inbound messages on a channel.

I guess these descriptions should be the other way around, they confuse channels and messages