What does verify return:1 mean in the openssl output

I don't understand the openssl output. Running openssl as follows:

#openssl s_client -connect google.com:443 -CAfile cacert.pem < /dev/null

Ultimately all is well in that the end entity's cert was verified OK: Verify return code: 0 (ok)

but what about w/the verify return:1 in the beginning of the output for the intermediates below? What does that mean or what is it's point?

depth=3 C = US, O = Equifax, OU = Equifax Secure Certificate Authority verify return:1
depth=2 C = US, O = GeoTrust Inc., CN = GeoTrust Global CA verify return:1
depth=1 C = US, O = Google Inc, CN = Google Internet Authority G2 verify return:1
depth=0 C = US, ST = California, L = Mountain View, O = Google Inc, CN = google.com verify return:1

---
Certificate chain
 0 s:/C=US/ST=California/L=Mountain View/O=Google Inc/CN=google.com
   i:/C=US/O=Google Inc/CN=Google Internet Authority G2
 1 s:/C=US/O=Google Inc/CN=Google Internet Authority G2
   i:/C=US/O=GeoTrust Inc./CN=GeoTrust Global CA
 2 s:/C=US/O=GeoTrust Inc./CN=GeoTrust Global CA
   i:/C=US/O=Equifax/OU=Equifax Secure Certificate Authority
---

The verify callback function (used to perform final verification of the applicability of the certificate for the particular use) is passed a field by SSL called the preverify_okay field that indicates whether the certificate chain passed the basic checks that apply to all cases. A 1 means these checks passed.

int verify_callback(int preverify_ok, X509_STORE_CTX *x509_ctx)

The verify_callback function is used to control the behaviour when the SSL_VERIFY_PEER flag is set. It must be supplied by the application and receives two arguments: preverify_ok indicates, whether the verification of the certificate in question was passed (preverify_ok=1) or not (preverify_ok=0).

This is what the verify return:1 is showing.

You can check the code if you want more details:

int MS_CALLBACK verify_callback(int ok, X509_STORE_CTX *ctx)
    {
    [ snip ]
    BIO_printf(bio_err,"verify return:%d\n",ok);
    return(ok);
    }