Spotting 15 days before period what it means?

Breakthrough: This is breakthrough bleeding and at 46 years of age it can be normal. One episode is likely due to hormonal shifts, but should it continue you should see a gynecologist to make sure that there are no uterine abnormalities or precancer risks. As we age, there can be greater swings in hormones and irregular bleeding patterns are common. If happens multiple times, see your doctor.

Ovulation: Given the timing of the spotting, midcycle, this is most likely related to a brief, abrupt drop in estrogen that occurs with ovulation. Given your age, greater than 40, you must have this evaluated by your ob/gyn. This evaluation should include an exam, ultrasound and endometrial biopsy!