Relationship between client_ssl property and client_certificate field in Service entity

Docs say:

Determines if Nginx should send client-side SSL certificates when proxying requ
Certificate to be used as client certificate while TLS handshaking to the upstrea
m server.

Which one will be used when they are both configured?
client_ssl is global scope, client_certificate will override it and it’s p
er-service basis. Is the understanding correct?