Some devices support only a discrete set of device ranges. When you specify input limits, NI-DAQmx coerces those values to fit within one of the supported device ranges.
For instance, suppose your device only supports ranges of 0 to 10 V, -5 to 5 V, and -10 to 0 V. If you set a maximum value of 8 V, NI-DAQmx coerces the maximum value to 10 V. NI-DAQmx also coerces scaled values, including custom scaling. If you have a temperature sensor that outputs 100 mV for every 1 °C, NI-DAQmx coerces a maximum value of 80 °C to 100 °C.
Because NI-DAQmx coerces input limits, code width is calculated based on the coerced values, which can be outside the minimum and maximum values you expect to measure.