Somewhere in the 7000 range is knowing where certain decks and deck matchups are going to end up at the end of the game. Hearing someone say, "This game will take 11-13 turns" always blows me away.
This isn't as hard as it sounds, and I think has something to do with how long you've been playing Dominion and reading the forums. These numbers came up more in the early days when Big Money was more prevalent.
Big Money only, no attacks: 4 provinces in 17 turns
Smithy only: 4 provinces in 14 turns
Moderately strong engine: 4 provinces in ~13 turns, plus endgame control
Super powerful engine: 11 turns
An example of a "super powerful engine" is the HoP megaturn game posted on the main DS webpage, Annotated Game #9 at
https://dominionstrategy.com/2012/01/20/guest-article-annotated-game-9/. Very few games go faster than 11 turns. So someone saying "11-13 turns" is saying that there is a LOT of engine potential on the board and things will go fast. If the engine is weak, it'll be 14-15 turns unless there is duchy dancing.
These numbers also illustrate why Big Money is such a plateau, and why the entire dominion community was "stuck" on BM for multiple years. On many boards with an OK BM enabler (many cards are at least as good as Smithy) and no attacks, the line between great BM play and great engine play is razor thin: one or two turns. Past that, the BM player has 5 provinces and the engine needs 4 duchies to compensate. It's hard to play engines that well, but it's easy to play BM that well.