after the first round of ammunition burns out, 7 is displayed on the panel, although the container is empty. You can see it in the screenshots.
There are six that survived in the hull ammo compartment plus one in the breech for a total of seven. IDK why they aren’t showing in the xray view. Look on the bug report page to see if its been reported already.
But I couldn’t shoot, I just didn’t have any shells.