Where are Signature Fields set for Worldpay

Woocommerce documentation on integrating with WorldPay (https://docs.woocommerce.com/document/worldpay/) says… “SignatureFields needs to be set using the same value from your WooCommerce settings” …but there’s nowhere to set signature fields in Woocommerce. Callbacks fail because the SignatureFields in Worlpay are supposed to match those in Woocommerce, but there’s nowhere to find them in Woocommerce.

Where are the signature fields set (or found) in Woocommerce?