The lower bowl is segmented. About 1/3 is for general tickets. That part is full. About 1/2 is for more expensive VIP tickets (not advertised anywhere I saw, but for sale at the venue at a table that is hidden below a staircase). That was about 10% full. The rest is behind the video board. A few boxes are occupied, the most vocal one by a group of Iranian fans. And just a smattering of upper bowl.
If you are in Belgrade and buying tickets daily, there is a ticket booth underneath the north stairs (near the gym) where you can buy Federation tickets for $55 instead of the advertised price of $70. They only take cash (dollars, dinar, or euros).
By saying "veterans of military service won" it is reasonable to assume the order of operations is veteran first, followed by title, rather than the other way around. However, the title could be read oppositely.