What modes do you have at the moment? Maybe BangGood got their stock mixed up and sent you an old version.

Default Biscotti modes, assuming nobody’s played with it before you got it: 0.1, 1, 10, 35, 100%, strobe, biking, battery-check.

There’s a way to recognise the most common old-model driver: put it in the lowest mode, wait about 5 seconds and see if it goes dim for a moment.