Error message
In the message, %s marks a value that the engine fills in when it raises the error.
The story
You asked rush to round a number, but the place you picked is out of reach. Here is the picture. Math.round counts places from the decimal point. Positive places count to the right: one place is tenths, two places is hundredths. Negative places count to the left: minus one rounds to tens, minus two to hundreds. Rush accepts places up to a million digits in either direction. That sounds like a lot, and it is. A place beyond that does not correspond to any digit a number on this heap could actually hold. Rush could have quietly used the nearest legal place, but then the result would round somewhere you never asked for, and you would not know. So it refuses by name, showing the places you gave and the legal range. Maybe a variable that was meant to be two ended up as two hundred million, because of a typo or a calculation gone wrong. The fix is to check where that value comes from, and pass a sensible number of places. Rounding should happen exactly where you meant it to, or not at all.
Text from the Rush engine's error catalogue.