Technically, there’s no limit of hobbies you can include, but you need to be smart about it. Like already mentioned, you can include up to 15 experiences under the “work and activities'' section.
The wisest idea would be to include 1 to 3 hobbies, and leave at least 12 spots to talk about other activities that should be prioritized above hobbies, like clinical work or volunteering. AMCAS application experts advise students to “enter only significant experiences since medical schools are interested in quality rather than quantity.”