SAMLP IDP: Request Template (optional)

I’ve set up a SAMLP IDP connection. In the configuration it has a field “Request Template”. Although it says it is “optional”, if I clear it it gets auto-filled again.

The autofilled template looks like this:
<samlp:AuthnRequest xmlns:samlp=“urn:oasis:names:tc:SAML:2.0:protocol”
ProtocolBinding=“@@ProtocolBinding@@” Version=“2.0”>
<saml:Issuer xmlns:saml=“urn:oasis:names:tc:SAML:2.0:assertion”>@@Issuer@@</saml:Issuer>

My experience with Auth0’s documentation is that it is very good. But I’ve been completely unsuccessful at finding any documention about this template - what is in it, what variables are available, etc.