Did he ever get it rechecked? I would definitely check it a few times to make sure it's really up and it wasn't something his body was fighting at the moment. If it's up over a period of time, I'd definitely see a hematologist. Is he concerned? Does he have any symptoms of a flare up?
I just looked this up though:
Somebody said...
How many white blood cells (WBCs) someone has varies, but the normal range is usually between 4,000 and 11,000 per microliter of blood. A blood test that shows a WBC count of less than 4,000 per microliter (some labs say less than 4,500) could mean your body may not be able to fight infection the way it should. https://www.webmd.com/cancer/white-blood-cell-count-low
11300 would be only slightly high if you go by that scale.