For each turn spent, you can claim about 13 acres of land.
You currently have 10,854 acres (44 acres unbuilt).

At 10,855 acres, it had dropped to 12 acres of land.



The chart inaccurately lists 10,854 as the beginning of 12 acres

Oh, so it's off by one? okie

i think how far off depends on the specific boundry, many are more than one ... but the tutorial message that says "explore rate will drop when we reach xxxx acres" reveals the proper boundries - that is, the message changes based on government type