How do i configure the values ?

[pidugusundeep]

How do i configure the values? i don't see any change in the widget even after changing the start and end positions, is there something else I need to set? btw iam trying to change these values

double _lowerValue = 10.0;
double _upperValue = 40.0;
int start = 0;
int end = 100;
int counter = 0;

[mvitolo]

Can you specify better the issue?
I have put your values in the example and works with no issue