How to set minimum time interval in `WorkManager`

I have set time interval in PeriodicWorkRequest 15 min but some time its executing before 15 min interval

This is my code

// START Worker

            PeriodicWorkRequest periodicWork = new PeriodicWorkRequest.Builder(LocationWorker.class, 15, 
            TimeUnit.MINUTES)
                    .addTag(TAG)
                    .build();
            WorkManager.getInstance().enqueueUniquePeriodicWork("Location", ExistingPeriodicWorkPolicy.KEEP, periodicWork);

Please suggest what i did wrong or how can I execute my code exactly after 15 min