Yes, that's the machine working area.
Plus over 8 inches in the Z axis.
It's MDF I use it as a work surface. It can get really trashed, so I replace it about every six months(depending on the workload).
I no longer add the grid, but it does illustrate the machine's capacity. At times I wish it was bigger, at the time I designed it I only had so much room.
But with CNC it doesn't matter, I break up larger parts and put them toghether later. There are different tricks to doing that, of course it depends on the part. Some parts I add slots or tabs, most of the time I use pins. The router drills the holes and I use the holes to locate the parts. I put the pins in the holes and then have fun sliding the part around till it drops on the pins.
Another thing to keep in mind when breaking up a larger part, is to cut the part short in the areas where the part has to be put together. I give about .004"-.008" depending on the material and what I'm going to do with the parts later. Another thing I do when assembling a larger part is to make a jig to position the parts for assembly.