Where does the extra Trample damage come from?

[Millefune]

I'm dealing with an Aurochs animal companion, and when it increases in size, it gets the Trample special ability. The trample damage is not listed in the Animal Companion information. So I went through the rules to find out what it should be, but I'm getting conflicting information. If you have the time, please help me figure this out?

Trample wrote:

As a full-round action, a creature with the trample ability can attempt to overrun any creature that is at least one size category Smaller than itself. This works just like the overrun combat maneuver, but the trampling creature does not need to make a check, it merely has to move over opponents in its path. Targets of a trample take an amount of damage equal to the trampling creature’s slam damage + 1-1/2 times its Str modifier. Targets of a trample can make an attack of opportunity, but at a –4 penalty. If targets forgo an attack of opportunity, they can attempt to avoid the trampling creature and receive a Reflex save to take half damage. The save DC against a creature’s trample attack is 10 + 1/2 the creature’s HD + the creature’s Str modifier (the exact DC is given in the creature’s descriptive text). A trampling creature can only deal trampling damage to each target once per round, no matter how many times its movement takes it over a target creature.

The "slam" damage for a large creature is 1d6 according to the Natural Attacks by Size table, but the Aurochs entry in the bestiary says the trample damage is 2d6.

Where does the extra d6 come from?

[Eridan]

The rules are written for PC classes and PC races. Dont compare monsters from the bestiary with the rules for PCs. There are some differences that are not explainable but that is the intent. Monsters are special :)

[Rynjin]

"Some creatures treat one or more of their attacks differently, such as Dragons, which always receive 1-1/2 times their Strength bonus on damage rolls with their bite attack. These exceptions are noted in the creature’s description."

Seems duly noted to me by virtue of it being different.

Looking at it, it seems to deal damage as two categories larger, not just arbitrarily increased. The Mountain Aurochs (Huge) likewise deals 2d8 instead of 1d8.

[Remy Balster]

Eridan wrote:

The rules are written for PC classes and PC races. Dont compare monsters from the bestiary with the rules for PCs. There are some differences that are not explainable but that is the intent. Monsters are special :)

You didn't understand the question, did you? Ha.

[Remy Balster]

This is an interesting oversight.

You could pull the trample damage from the bestiary entry, that seems fairly reasonable.

But it also seems reasonable to calculate the slam damage listed from the trample ability via creature size.

Unfortunately, since those two figures aren't the same...

You have yourself an interesting dilemma.

[Ipslore the Red]

I believe JJ himself has said that the bestiary rules for damage dice almost never actually apply in practice. For example, rock throwing. If I recall correctly, no creature with rock throwing has the same dice the book says.

To answer the question, it comes from the Bestiary rules not being able to cover every scenario. It probably shouldn't have been written in the monster Bestiary with how often violated it is, but hey.