You can inspect the key details of your certificate by running:

step certificate inspect --short myservice.crt

It should look similar to this:

X.509v3 TLS Certificate (ECDSA P-256) [Serial: 2441...2018]
  Subject:     myservice
               admin@yourco.com
               <https://auth.smallstep.com#98496ed4-7f27-4367-b7a2-ef828e0a4eda>
  Issuer:      Dev Intermediate CA
  Provisioner: authority-admin [ID: 909d...8521]
  Valid from:  2022-03-08T13:41:15Z
          to:  2022-03-09T13:42:15Z

If interested in the full certificate details, leave off the --short flag from your call:

step certificate inspect myservice.crt

It will look something like:

Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number: 174722835395825118890075525124613812754 (0x837264e17d78728efd82c16480a13212)
    Signature Algorithm: ECDSA-SHA256
        Issuer: CN=Dev Intermediate CA
        Validity
            Not Before: Mar 8 13:41:15 2022 UTC
            Not After : Mar 9 13:42:15 2022 UTC
        Subject: CN=myservice
        Subject Public Key Info:
            Public Key Algorithm: ECDSA
                Public-Key: (256 bit)
                X:
                    79:1e:ef:39:88:9e:20:fc:66:db:d2:a6:1b:e1:c9:
                    00:9c:cf:fb:67:b5:3c:08:ae:0b:4e:2d:8d:04:f6:
                    a8:0a
                Y:
                    62:ed:fc:be:34:d5:42:5d:da:c5:89:3f:38:67:5b:
                    60:98:d0:29:68:d2:a8:f9:8c:c3:13:02:94:e4:a4:
                    1d:73
                Curve: P-256
        X509v3 extensions:
            X509v3 Key Usage: critical
                Digital Signature
            X509v3 Extended Key Usage:
                Server Authentication, Client Authentication
            X509v3 Subject Key Identifier:
                78:E5:C6:20:54:34:27:27:FA:0E:75:0C:DE:DA:51:E1:12:CB:41:14
            X509v3 Authority Key Identifier:
                keyid:F8:2F:07:DB:83:F3:2D:67:51:45:F4:D0:14:82:51:14:BF:6D:4F:02
            X509v3 Subject Alternative Name:
                DNS:myservice.internal.mycompany.net
            X509v3 Step Provisioner:
                Type: OIDC
                Name: authority-admin
                CredentialID: [ID: 909d...8521]
    Signature Algorithm: ECDSA-SHA256
         30:45:02:21:00:f0:1e:ff:45:68:15:3e:3f:a7:0c:77:9b:03:
         9c:80:27:10:e9:e4:36:57:fb:19:4b:56:c1:eb:5d:cc:56:7f:
         ea:02:20:25:a2:c4:ec:cb:fb:c6:0f:ce:8f:df:cc:65:e1:aa:
         42:f2:87:b4:8a:c7:22:fd:67:3d:2f:53:08:57:ef:25:35