The Order Fulfilled trigger starts a series of actions when an order on your Shopify store has been fulfilled. Use this workflow trigger to notify contacts or send internal notifications to clients. To use it, click Add New Workflow Trigger and select Order Fulfilled.
Filters
You can customise it further by clicking Add Filters.
Cart Value
The Cart Value filter lets you set a cart value with specific customisations.
To trigger the filter, provide a condition such as cart value is greater than $500. 
Once the filter is set, click Save trigger. From there, add any actions you'd like the workflow to carry out. Remember to click Save in the top right corner to keep your changes, then switch your workflow to Publish when you're ready to go live.