This charger can't provide anywhere near the max continuous charge current of a Samsung 25r.

Whatever li ion setting you use will be fine.

Anything below 2.8V is an overdischarge, but 3.2V is a good minimum for most any li ion cell.

Then again, if you use mechanical mods, most of us notice a major performance drop at the 3.7V-3.4V range, which is why most of us charge our power cells at that time.