"Exclusive Mode" allows a specific application (like a DAW or high-res music player) to take full control of the audio device, bypassing the Windows mixer for lower latency and "bit-perfect" playback.
In the context of Windows audio (WASAPI – Windows Audio Session API), "Exclusive Mode" is a permission given to an audio application to take complete, sole control of the audio endpoint (your AB13X DAC). ab13x usb audio driver exclusive