Medicinal Dosage of Ginger for Digestive Problems

Can you please tell me just how much ginger a person can take for digestive problems such as flatulence? My mother had a stroke 2 months ago. From being in the hospital and rehab at the nursing home, she ended up with clostridium difficile. Antibiotics cleared it up. Some ginger every day shouldn't hurt her but I need to know the proper amount.

The medicinal dosage of ginger is one quarter teaspoon of powder in a cup of boiling water, three times daily with meals. Alternativley, the ginger can be cooked with food.