I don't believe these recommended specs were published with a specific level of concurrency in mind, but I would expect such a machine to easily support 15-20 concurrent, active users. Your specific mileage may vary significantly, though, depending on the complexity of your apps.
At a certain point, it becomes more economical to scale horizontally instead of pumping up the specs of a single VM. There's a lot of nuance to this topic, but you can read a few tips here.