Look at your assignments for Armored Kill and it will tell you how many kills you have with both mobile artillery and tank destroyers. Or, you can check on THIS
website, which shows that you have zero kills with each.
163/164 games completed (including DLC)
Completion percentage: 100%
Latest retail completion: Dragon Age II
Latest arcade completion: Dust: An Elysian Tail
Currently Ranked #1 on Achievement Completion Percentage Leaderboard on TA