For slot determination at spawn, is there an intensity number that is the "border" for each slot tier? If so what are they?
These numbers are approximates, as it is all based on lots and lots and lots and lots of time spent in the field loring various animals to find ranges.
1 Slot: 0 to 2705
2 Slot: 2705 to 4254
3 Slot: 4255 to 5760
4 Slot: 5761 to Unknown (more data is needed, somewhere around ~7400 I believe. The only things that currently spawn as 4 or 5 slot are Greater Dragons and Dragon Turtles, which are pretty uncommon to find so data is limited.)
This is
at time of spawn intensity. If the pet engages in combat after spawning, or you skill it up after taming it, and it naturally raises it's Stats (Dex/Stam/Int/Mana) to 125, they can potentially become an over-imbued pet. Meaning they will rate over 100%. The rating is still a fair assessment of the pet's power in this case, as the rating is based purely on the spawn potential.
Someone recently sent me a Najasaurus they had tame that was rating as a 10% 3-slot pet, but the lore page showed it was a 2 slot. Turns out it was an incredibly high 2-slot spawn, with next to nothing in Int/Mana. He then skilled the pet up naturally, which raised it's Int/Mana to 125, giving it about 100 free intensity. Once I accounted for this in the calculator, his Naja was rating as a 116% 2-slot in its current state.
So if you look at the ranges above, and look at a pet that has a spawn intensity of 3000, vs a pet that has a spawn intensity of 4200 -- they will both be 2 slots, and they will both have 3 full levels of training. But the pet that spawns as a 4200 has ~1200 more intensity for the same slot, which is a huge advantage (unless that intensity is eaten up by Magery/Necro).