It can be hard to determine the cause.
I've had elevated WBC for a long time, before beginning T. I should probably get my levels checked again, the odd thing is I haven't had a day sick in years, and high WBC count usually follows an infection of some kind. Doc told me it could be stress, it could be cancer, it could be viral, could be anything basically, but if they've told you the levels are not high enough to worry about then I guess there's no cause for alarm. I do take vitamin B8 which is supposed to directly enhance the immune system, which could be it, but I suspect not since taking it is something I've only done in the last year.