It can be anything! An apex, subdomain, or even a URL.

Results forbeta.convenio.app

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2020-08-23T20:58:23.326	2020-08-23T19:58:22	2020-11-21T19:58:22	www.akasaka-bento.tokyo	beta.convenio.app	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-08-23T20:58:22.69	2020-08-23T19:58:22	2020-11-21T19:58:22	www.akasaka-bento.tokyo	beta.convenio.app	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-06-25T15:53:53.469	2020-06-25T14:53:53	2020-09-23T14:53:53	slateco.io	beta.convenio.app	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-06-25T15:53:53.323	2020-06-25T14:53:53	2020-09-23T14:53:53	slateco.io	beta.convenio.app	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-06-25T13:24:48.073	2020-06-25T12:24:47	2020-09-23T12:24:47	beta.convenio.app	beta.convenio.app	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3
2020-06-25T13:24:47.848	2020-06-25T12:24:47	2020-09-23T12:24:47	beta.convenio.app	beta.convenio.app	C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3