LineTracker Sensor reporting

I’m trying to calibrate my line tracker by find the threshold value using this code, but what reports back is 2^32 (4294967296 ) for both percentage and analog. What does that mean?

My code:

while(true) {
Brain.Screen.clearScreen();

// display the line sensor percent value on the screen
Brain.Screen.printAt(1, 20, "percent: %f %%", LineTrackerH.value(percentUnits::pct));
Brain.Screen.printAt(1, 40, "analog: %f mV", LineTrackerH.value(analogUnits::mV));

//Sleep the task for a short amount of time to prevent wasted resources.
task::sleep(10);

}