How the hell did this happen.

I attack a city with lvl 5 archery and 500 Archer towers with 425 Ballista at lvl 7 archery and only take out 20 towers.

What is wrong withthis picture?

battle25.evony.com/default.html?logfile/22/4d/0e/8d/224d0e8de444e603f67bfe99c457dabb.xml

If anyone can explain this I would be grateful.