#1 thing to do before you turn the light on while powered from your bike is put it in “e-bike mode”. There are instructions to do it in the thread.
You will not get the max lumens out of the light in e-bike mode. E-bike mode reduces the power output of the light to prevent too much current...
Also, 1 ball is smaller than the other 5. A caliper will be needed as it’s not obvious which is the smallest. The 1 small ball is the same as the ball already on the shock so it can be used or discarded.
It was a battery for a different magic shine light I had.
Try turning the bike on and holding down the lights power button for 8 to 10 seconds to get it to ebike mode. The button on the light should flash red once in ebike mode.
There is an Ebike variety for the ME2000 which is cheap because it doesn’t come with a battery. Make sure to order the Brose power cord with them. I’m not sure on Lupine.
Also, the green plug is for powering a front light.