RandomSpawner.cs

// Start work from the list/collection/array of all "CurrentAmmoSpanPos", which are the spawners
var spawners = CurrentAmmoSpanPos.Select(spawner =>                        // Create an "anonymous" type, which generates an object with properties
                                                  new {
                                                        // Save the spawner, so we can use it later
                                                        Spawner = spawner,
                                                        // Calculate the distance between the player in that 
                                                        Distance = Vector3.Distance(Player.transform.position, spawner.position)
                                                      }
                                          ) 
                                  // Order all the items by position, smallest (closest) to biggest (furthest)
                                  .OrderBy(pos => pos.Distance)
                                  // Don't use the one in 1st place (closest)
                                  .Skip(1)
                                  // Take the next 3
                                  .Take(3)
                                  // Make it a list. Array may be better?
                                  .ToList();  // .ToArray() to make it an array
                                  
var pickedSpawnPos = spawners[RandomInt(0, spawners.Count)]   // Get the random spawner between 1-3 (0-2)
                          .Spawner        // Pick the spawner that we saved earlier. We could also see ".Distance" here
                          .position;      // Get the ".position" property of the spawner, because it's what we need.
                          
return pickedSpawnPos