Are NP6 XAUI links are 10Gbps full-duplex?

Hello,

fortinet docs says the following about NP6 XAUI links:

Each NP6 processor has a 40-Gigabit bandwidth capacity. Traffic passes from the interfaces to each NP6 processor over four XAUI links. The four XAUI links each have a 10-Gigabit capacity for a total of 40 Gigabits.

https://docs.fortinet.com/document/fortigate/7.2.0/hardware-acceleration/737486/optimizing-np6-performance-by-distributing-traffic-to-xaui-links

Is this information meant as a total bandwidth or as a bandwidth per direction (full-duplex), meaning 10 Gig for RX and TX each?

thanks in advance

Best regards

Hakan