The LAZY mode would behave similarly to a service which initially has a mode of ON_DEMAND and has the following code:

// ...
   public void start(StartContext ctxt) throws StartException {
      ctxt.getController().compareAndSetMode(ON_DEMAND, ACTIVE);
      // ...
   }

   public void stop(StopContext ctxt) {
      ctxt.getController().compareAndSetMode(ACTIVE, ON_DEMAND);
      // ...
   }
// ...

In other words, the service only starts when demandCount > 0, but once it is up it will stay up until forced to stop by mode change or by stopping dependency, at which time it will again require demandCount > 0 before it comes up again.