Need help with calculating damage for ligneous instinct Barbarian

Hey guys, new GM here.

I've had trouble understanding the damage output of my lvl 1 barbarian in my party. He wields a Greataxe and chose Ligneous Instinct. I put together the character in Pathbuilder2e.
As he has +4 Strength and is proficient with Greataxe the damage per Pathbuilder without rage is 1d12+4. As I understand, the +4 comes from his strength modifier.

So, when he rages he gets +2 damage, and if he is using ligneous instinct, it states that for a speed penalty of 10ft he can increase his rage damage from +2 to +6. Does that mean that if he does so and hits an enemy he does 1d12 + 10 damage at lvl 1? While the rest of the party maxes out at 10 damage per hit with a max roll, he does 10 flat damage right off the bat and 22 damage on a max roll. Am I missing something or does he just hit that hard?