A randomized controlled trial was conducted to evaluate the safety profile of Drug X in patients with chronic atrial fibrillation. 200 patients were randomized to receive Drug X, and 200 patients received standard therapy without Drug X. Over a 1-year follow-up, 20 of the 200 patients in the Drug X group developed major gastrointestinal bleeding, whereas 10 of the 200 patients in the control group experienced the same adverse event. Calculate the number needed to harm (NNH) for Drug X based on these results.