Are you taking medication?
I am on Carbimazole for Graves Disease, and my white cell blood count is often low as a result. I also suffer from Pernicious Anaemia, which can affect the results too.
They can get really quite low before you'd notice without a test. If they are picked up by a routine test and you wouldn't have gone to the doctor yourself, I wouldn't worry.
Obviously it's better if these things are in range, but they are more for medication control than an indicator of something in themselves, if that makes sense? My results are used to determine whether I need to alter the dose of my medication.