They are referring to the volume up and down buttons on the device. Actual buttons, not anything that would be on the screen.
Yeah, it is quite odd that they don't have psyical buttons. Here is how you can reset these tablets.
Option 1...
1. Disconnect your tablet if it is connected to a computer.
2. Press and hold the POWER key for about 10 seconds to turn off the tablet, and then press and hold the POWER key to turn on the tablet.
Option 2...
If that doesn't work, then you can try the following...
https
/youtu.be/HcQIDg8jAFw ...it shows another way to try it, but this does involve a computer and some downloads.