The NFT ID or Serial Number(curiously it's one number less than the number out of 1000 that applies to my card)
This will NOT always be the case, especially with Collections that have multiple Rarity to them.
With this NFT, it jus so happens to be coincidental.
All Collection start with ID 0
And this ID 0 is usually assigned to Serial Number 1
So the NFT ID is One Less than the Serial Number of your Card.
Now let's explore what happens when there are 1000 Legendaty NFTs and 400 Epic NFT's ond 250 Rare NFT's
all in the same collection...
The NFT ID's of the Legendary cards are rom 0 to 999 - that is 1000 cards
then the NFT ID's of the Epic cards are from 1000 to 1399 - that is 400 cards
and the Rare card ID's are from 1400 to 1649 - that is 250 cards.