Discount is not a standard field on the Opportunity object, so you need to create a custom field to capture the discount amount or percentage for each opportunity. To set up an approval process where opportunity discounts over 30% need to be approved by the VP of sales, and any discounts above 10% need to be approved by the user's manager, you need to configure two separate approval processes with different entry criteria based on the discount field value and different approvers based on their roles. References: https://help.
salesforce.com/s/articleView?id=sf.approvals_getting_started.htm&type=5