For now.. ignore the "smart" part of the charger ... It just means it has a computer controller and has no other "magic" to it. Think of is just as a standard charger that can monitor itself, whether it better than other controlled chargers is probably up to debate ( although I'm not certain )..
So the storage setting is just there to get the battery back to a storage charge. On LiPo's that's usually about 3.6v-3.7v per cell more or less. How long it takes to get to a storage charge level will depend on several things... First the voltage and capacity of the battery. Second if the battery has more voltage or less than the storage voltage. If the battery is lower than the storage voltage, then it will need to be charged up to it. If it's higher than the storage voltage it will need to be discharged down to it. Typically chargers can charge up much faster than they can discharge... but each one is different so I'd refer you to the manual for those specs. Many hobbyists will try to discharge their batteries down to about a storage voltage on their last flight or run since it's much faster than trying to use a charger which must use a resistor pack to do the same thing.
Typically you would place your batteries into storage "mode" anytime you aren't going to be using them within a day or three. This extends the potential life of the battery. So if it's going to be a week or so... get there voltage down ( or up ) to the recommended storage voltage for the cells you have. It's best to not recharge them to full charge until you are ready to use them again or no longer than the evening before.
