iTunes chooses only a small number of categories from the ones you specify. Generally, this is done in alphabetical order.
Pinecast recommends that you do not choose more than three categories. Do not choose a category if you would be uncomfortable having your podcast listed exclusively under that category. After updating your category choices, Apple will automatically refresh your feed after about a day. If you need to update it faster, you can manually refresh your feed through the Apple Podcasts Connect portal.