Ok I bought an istick mini 10w and vapes out of the box until the battery was dead. Charged the battery until the display no longer showed % just like the paper that came in the box said. Took it off the charger and started vaping 3-4 puffs later the display reads 81% then 3-4 puffs later goes back to 100% then after the next puff it reads 99%. I'd there a problem with this device? I've tried google and nothing about this comes up? Should I just ignore it and keep vaping or try to exchange it bought from mad vapes if that matters