Vitamin D level
First, when you get lab values, you need to get the units it's measured in, in this case either nmol/l or ng/ml since the numbers for "normal" vary accordingly.
Also, do not be afraid to ask your doc what that value means. I'm assuming it's 12 ng/ml, which is just above the cutoff point for "deficiency" and still in the "inadequate for bone and overall health" range. Ask doc about supplements