It's an Android Lenovo again. Hard reseting Lenovo IdeaTab A2107A-H is different from hard resetting Lenovo P700i. You will know later the difference. Again back up all your datas or files. Do not make a hard reset when you smart phone has empty battery. If that's the case, you should recharge first your battery.
How To Hard Reset Lenovo IdeaTab A2107A-H
1. Hold or press both Volume Up and Power On button and unpress it when the Recovery Menu shows.
2. You will see choices. Use volume button to choose the "clear emmc"
credits to Xeven2nd for the images