Why does the "Issued by" field in github certificate show my organization name

Question

When I view certificate of website https://github.com/pre-commit/pre-commit-hooks from my company's laptop I see following details

Issued To
    Common Name (CN)        github.com
    Organization (O)        GitHub Inc.
    Organization Unit (OU)  <Not Part Of Certificate>

Issued By
    Common Name (CN)        gp.myOrg.com
    Organization (O)        myOrg LLP
    Organization Unit (OU)  Network Information Security

whereas when I view the same vertificate from my personal laptop I see:

Issued To
    Common Name (CN)        github.com
    Organization (O)        GitHub Inc.
    Organization Unit (OU)  <Not Part Of Certificate>

Issued By
    Common Name (CN)        DiiCert TLS Hybrid ECC SHA384 2020 CA1
    Organization (O)        DigiCert Inc.
    Organization Unit (OU)  <Not Part Of Certificate>

To trust a website I would ensure the certificate issued to website is by well known CA. When vieweing certificate from company's laptop why would it show that certificate to github was issued by company's CA?

Can someone explain this and also provide reference to good documentation explaining this.

Thanks in advance.