premise: How to help prevent epidemics from spreading<br>Wash your hands when preparing food or going to the bathroom. Practice good hand hygiene by washing your hands with antibacterial soap and water for at least 20-40 seconds. Make sure you wash your hands before and after you prepare food as well as before and after you go to the bathroom to prevent the spread of germs.
hypothesis: Half a minute is a good duration for hand washing
reason: The statement says that you should wash hands for 20-40 seconds. 30 seconds fits within that frame perfectly making my statement correct. The model might have been confused by the sentence structure.