If the TouchPad screen is subjected to excessive pressure for an extended period of time temporary pattern of rings may appear on the screen. This phenomenon is called ring marks and is inherent in the touch screen technology used in the TouchPad as well as other tablet devices.
These ring marks normally fade in a few minutes with no adverse affects to your TouchPad. If the ring marks do not fade within a few minutes try attaching the power cable, which may reduce the time for the rings to fade. Note that if the TouchPad is again subjected to excessive pressure the ring marks may reappear temporarily.
This is not a reason to return the TouchPad; as noted this is inherent in the design. There may be, however, some cases in which the ring marks do not fade away. If the ring marks do not disappear on their own, or after attaching to power for 10-15 minutes, an exchange may be necessary.
To prevent reoccurrence avoid squeezing the TouchPad into a full backpack or briefcase or setting heavy objects on the TouchPad screen.
If the ring marks do not go away you should contact HP support for further assistance.
(Do note at this time I can not see the pictures very well, so this may not be entirely accurate).