Grounds in your cup are generally caused by water overflow.
To prevent this, try and adjust the "Water" slider under "Customize drink".
Depending on the recipe you have digitally scanned from the Marketplace, the amount of water may differ. The sliders give a good indication of how much water will flow into your cup. Also, as taste preferences vary, the customizability of the sliders gives each user a unique choice!
Should there still be noticeable coffee grounds in your cup after having adjusted the sliders, please contact Spinn for further assistance.