Outside air and "port" for Hybrid Stove

Hi Max and everyone,

I’m finishing up a foundation for the Hybrid stove and am at the stage of placing the top slab of the foundation. I’ve decided to try to work in an outside air intake (a 6" round duct) and am thinking through the placement of the duct in the slab. My instinct is to offset it to the firebox side of the stove so it’s directly under the grate and a bit towards the rear of the plan in the N-S axis. On the drawings, there’s a note for a “port” on Section 6 and I’m guessing this is a secondary air port behind the firebox, but I’m not totally sure what’s all being called out on that drawing. Where would that “port” air normally enter from in a build that didn’t have any outside air, behind the ash box, somewhere else?

Thanks for any advice!