When you become a patron to a creator who is charging per-post, you have the option of setting a monthly limit to your payments. This prevents you from being charged more than you're comfortable, if the creator makes several paid posts in a given month.
If you have never made a payment to the creator:
If you already have a payment to a creator and forgot to set up a monthly limit:
You'll be able to add a monthly max to your membership at anytime. You can also edit or remove your monthly max if you'd like.