Is this a bug? Among 28k soldiers only 24k is sieging Trondelag and the other 4k have black flag and can't fight. I don't see how it could happen in real life - アニメと動画配信について教えてください

Is this a bug? Among 28k soldiers only 24k is sieging Trondelag and the other 4k have black flag and can't fight. I don't see how it could happen in real life