Hi!Duhui, I hope this help you
1. You can query your solution for the "FacilityRank", number 1 is the best solution in the closest facility analysis or you can configure how much facility you need in "Advanced Setting/Facility to find" if you need the best solution, you should put the number 1.
2. When you have the last analysis, you should make service areas that you need and you have two options, select by locatión all the destination within every service area, or you could an spatial join to fill a field with service area distance or driving time.