Input limits are the maximum and minimum values you expect to measure, after any scaling, including custom scaling.
Input limits are sometimes confused with device range. Device range refers only to the input range of a particular device.
If you set your minimum to 0 and your maximum to 7, and your device only has a 0-5 and a 0-10 device range, the device range will be coerced to 0-10 by NI-DAQmx. This also applies when using a custom scale.
The maximum and minimum input limit values will match the units of measurement of the task. For instance, the device range for a DAQ device might be 0 to 10 V, but that device might be used with a temperature sensor that outputs 100 mV for every 1 °C. The input limits in that case could be 0 to 100, with 10 V corresponding to 100 °C. For an analog current input task, the units would be amps.
Input limits in a smaller range can improve the precision of your measurement. If your device has multiple input ranges, you can strategically choose the minimum and maximum values to detect smaller differences in your signal of interest. Consider a device that has a 0-10 V and a 0-5 V range. In the previous temperature sensor example, if you knew that the temperature would never be higher than 50 °C, you could choose a minimum value of 0 and a maximum value of 50. The device can then detect smaller differences in temperature because it is digitizing a voltage between 0 and 5 V, rather than 0 and 10 V.