to format your Lenovo ThinkPad tablet to the factory settings please follow the steps bellow accurately :
note :before performing the hard reset of the Lenovo thinkpad tablet make sure you have a system backup , because all of your data will be lost during the process.
1-turn off your thinkpad tablet , press and hold the power button to turn your tablet off
2-press and hold the power button until the tablet vibrates .
3-keep pressing and releasing the volume up button until the booting loader screen appears, may be after the second volume button pushing.
4-then you will get android system recovery <3e>
5-use the volume down button to scroll to Swipe data /Factory reset then press the power button when you reach the swipe data/factory reset
6-confirm the factory reset by scrolling down using the volume down button to yes-delete all user data
7-then after finishing the factory reset the reboot system now choice will be highlighted press the power button .