First, you are posting in the wrong forum. This belongs in the QCRTGraph for java forum.
The Java definition for Double.MIN_VALUE is the smallest possible positive number not equal to 0. The software is clamping the values less than zero to this value, which is what it should do. You are correct that the default minimum allowable value should not have been set to this value.
While -Double.MAX_VALUE would work, why aren't you choosing a value which is closer to the minimum in your your valid range of values, such at -10 in a (-10 to 10) range, or -200 in a (-200 to 1476) range.