I have a JuiceBox 40. From the JuiceBox app, you can set two timers - one for weekdays and one for weekends. It's pretty simple, you set a time to start charging and a time to stop charging. I don't use this feature, but I assume what it does is shut off the power to the vehicle outside of the charging window. So if the vehicle reaches its target state of charge (SOC) during the charging window, it will stop charging. If it doesn't reach the target SOC, then the JuiceBox will cut off power to the vehicle and force it to stop charging at the end of the charging window. This makes sense if you're more concerned about avoiding times of day with higher electricity rates than you are about reaching the target SOC. My electricity rates don't change with time of day, so I will only use this timer if our utility asks users to conserve energy which they sometimes do during the hottest summer afternoons. In that case, I might set the JuiceBox timer to allow charging from 10:00pm to 6:00am then plug in the vehicle set to charge to 80% through MMI or the MyAudi app. In that case, charging would begin at 10:00pm and end at 80% SOC or 6:00am - whichever occurs first.
The JuiceBox has a separate function that allows you to enter the starting range in miles and the target range in miles. Note that you have to enter these figures manually because Level 2 EVSEs do not know what the vehicle's SOC is at any given time, and they only know the theoretical range rather than the vehicle's guess-o-meter range which is always changing. Presumably this function will turn the power to the vehicle off when the EVSE has determined that the target range has been achieved. I don't use this function because a) you have to manually input the starting range, b) both the starting range and the target range vary due to ambient temperature and the efficiency of your recent trips and the EVSE doesn't account for this and c) I'd rather think in terms of percentage SOC than range because that's how Audi recommends you preserve battery life (i.e. don't charge past 80% unless you need to). I don't find this function helpful at all, but you can't disable it so instead I set the current range to 0 and the target range to 222 miles no matter what the SOC is when I plug in so that the vehicle decides when to stop charging rather than the EVSE making that decision.
Additionally, smart EVSEs like the JuiceBox presumably can be controlled by your utility in exchange for lower rates. In that case, I assume the utility manages the charging window for you and it functions like the first example above.
The smart EVSEs do give you additional timer options, but they are limited because Level 2 EVSEs don't share data with the vehicle. I like the JuiceBox for other reasons (especially the 25' cord, the ability to vary the amperage and the additional energy usage metrics).