Welcome to the community @EthanG 

You can achieve this in Klaviyo:

• Create a 10% dynamic coupon for your >$500 abandoned order value. For example, name this code ‘10PC_500_abandoned_flow’. More info on dynamic codes here and specifically for Shopify here
• Add a trigger split in your abandoned flow with a configuration of ‘$vaue is greater than 500’ immediately after the ‘checkout started’ trigger (see below).
• In the abandoned cart messages in the trigger split YES branch include ‘{% coupon_code '10PC_500_abandoned_flow' %} in the email body where you want it. On email send, Klaviyo will insert a unique 10% code for each recipient.

Assuming you’re sending multiple emails in your abandoned flow, I suggest not offering the discount in your first email - too soon in my opinion - plus make the discount time-limited to increase fear of missing out.

You may also want to configure the flow so a contact doesn’t get a discount every time they abandon checkout. That may encourage them to to abandon in future. 

Also, set your flow to manual initially so you can review the contacts in each message’s waiting state to check all is working as you’d expect before setting to live.

Hope that helps

Andy