Venom Immunotherapy CPT® 95145-95149

I would appreciate any guidance anyone can provide on the billing of CPT® codes 95145 - 95149. Our physician has a patient on Mixed Vespids (Yellow Hornet, White Faced Hornet and Yellow Jacket) and Wasp Immunotherapy. I believe this would be seen as 4 single stinging insect venoms = 95148. How many units should this code be billed with? I see that in the code description it states to "specify number of doses" but I'm not clear on what that means. Can anyone help explain? Thank you!