Gravity EMG Sensor Returning Massive Values

Hello! I recently purchased the Gravity: Analog EMG Sensor by OYMotion for a school project. Whenever I attempt to calibrate the sensor (using the code found here) it returns values that are way too high. You can see some of the output in the included screenshot. I've tried moving the sensor around my arm, but no position seems to be working. It keeps returning these random values even when completely removed from the skin. I'm using the Arduino IDE software, and connected the sensor to an Arduino UNO R3 board. The board itself is connected to my laptop, which I have running on battery, not plugged in to anything. Can anyone help fix this issue? Thanks