300mah low mode should charge your batteries in approx 8.5 hours
500mah normal mode should charge your batteries in approx 5 hours

Most of the charge rates of batteries used for vaping are high enough for you not to worry about if your using a nitecore charger.

I only use the low mode for when I charge AA or AAA NiMh batteries all my vaping batteries I just turn on the charger and put them straight in and don't worry about the buttons but I still keep an eye on them as you can never be too careful