Any good tips for ground attack missions on sim ?

[Yossarian]

Right I've done the Stalingrad campaign but what was very confusing was the the total of armour targets that I had to destroy in the bottom left hand side of the screen never ever went down even when I was getting the messages 'direct hit' and 'target destroyed'. Just as I was about to give up the total targets to hit indicator just disappeared and after a while and I was given my next objectives, confusing and frustrating..