How to calculate the Carrying Capacity of the [Snake, Constrictor]?

I have a [Snake, Constrictor]（Strength 24，Large），how to calculate the Carrying Capacity？
It's Carrying Capacity is 699/1398/2100 ？

its counted as a large quadrupedal for carrying capacity, so x3 normal carrying capacity

How can it be a quadruped when it has no legs at all?

it's based off of it's body, large and above "long" types are always considered quadrupeds regardless of how many legs they actually have

May I see the rule that says that?

Bigger and Smaller Creatures: The figures on Table: Carrying Capacity are for Medium bipedal creatures. A larger bipedal creature can carry more weight depending on its size category, as follows: Large ×2, Huge ×4, Gargantuan ×8, Colossal ×16. A smaller creature can carry less weight depending on its size category, as follows: Small ×3/4, Tiny ×1/2, Diminutive ×1/4, Fine ×1/8.

Quadrupeds can carry heavier loads than bipeds can. Multiply the values corresponding to the creature's Strength score from Table: Carrying Capacity by the appropriate modifier, as follows: Fine ×1/4, Diminutive ×1/2, Tiny ×3/4, Small ×1, Medium ×1-1/2, Large ×3, Huge ×6, Gargantuan ×12, Colossal ×24.

Because that is the only text I could find mentioning about large creatures.

For whatever its worth, the mount for the First Mothers Fang Cavalier archetype has this to say for its serpent mount "A serpent mount is considered to be a quadruped for the purpose of determining its carrying capacity,"

To me, that sort of kind of vaguely implies that a NORMAL giant constrictor snake would NOT be considered to be a quadruped (if it was, why explitly add that clause?). But that line of argument is, IMO, not exactly conclusive

In any case, snakes of size Large and above seem to have "tall" rather than "long" reaches. See the Emperor Cobra and the Giant Anaconda for examples.

To me, that sort of kind of vaguely implies that a NORMAL giant constrictor snake would NOT be considered to be a quadruped (if it was, why explitly add that clause?).

Because it is an oddity that never gets mentioned in books because players generally are not snakes, and 'how much can it pull' is not generally asked about monsters.

Telling you how much a snake can carry in an archetype revolving around being carried by a snake is reasonably a clarification of intent.

Kind of an "FYI, snakes carry as much as horses" Vs "This snake is special in that it can carry as much as a horse" debate.

The answer to this question is very important to a summoner with a serpentine eidolon.

reverse engineering the numbers shows that it counts as a large quadrupedal creature divide its carrying capacity by 3 and you get the numbers for a medium bipedal creature with 24 str