For a typical breaker, especially a thermal mag breaker, it is typical for the left side of the curve in the long time pickup region to reach the "trip" value at about 1000 seconds with an ambient of 40 deg C.. It is also typical for the left side of the curve in the instantaneous region to be at 10-12 times the "trip" value. The only aspect of the curve that get affected by different ambient conditions is generally the long time pickup/delay portion of the curve (approx above 10 seconds).
The thickness of the curve (left to right above .02 seconds) is manufacturers tolerances permitted. So depending on which batch you have, the current to trip the breaker at 1000 seconds, may be as much as 1.4 x the "trip" value.
Again generally, instantaneous trip is for short circuits, and long time trip characteristics is for overloads.
For solid state breakers, there is also another characteristic between long time and instantaneous, which is short time pickup/delay.
