The only case when you could be receiving approximate coordinates is when these are GSM coordinates, not GPS. This means that Monimoto was not able to catch satellite signal to determine the exact location, so it was forced to use different technology - CellLocate® to determine it.

What's the reason for the inaccurate coordinates?

Incorrect installation might be the reason causing the poor signal. Please see correct installation instructions here. If your Monimoto is already installed in a motorcycle or other vehicle - please check if it's thinner end is facing outwards rather than inwards, or towards the ground.

Another reason could be that your Monimoto is indoors. GPS signal does not work properly when the receiving device is indoors.