How the heck does the ballista elephant's damage work?

So, i've been doing some tests for a video, but I can't freaking figure out how the damage works. To start off, it seems to not want to hit targets, which makes it difficult. Anyway, in post imp it always deals 10 damage at most per shot. It has 10 damage, and accordint to SOTL it does 10 damage -armor vs all untis (not halved vs secondary targets like scoprion). However, this means the second bolt must not be doing damage! However, the unit that is the farthest away (the last one to get damaged gets dealt 16 damage (with no Pierce armor)! What the heck is going on! -Tests done with voobly.