The data starts at 0m, but echoes within the sensor head after a transmission take a while to die down, which means that there’s noise in the readings up until about 0.75m, so reflections off external objects within ~0.75m of the sensor can be difficult to see/detect properly.
This image gives a sense of the noise from internal reflections when the sensor is scanning a 2m range:
Note that when the scanning range is set to longer the transmitted pulses are also longer, and the echoes take a bit longer to die out.