From https://code.google.com/p/google-authenticator/wiki/KeyUriFormat#Issuer "We recommend using both issuer label prefix and issuer parameter together to safely support both old and new Google Authenticator versions."
I changed the email to user_login before I added the issuer parameter because the label and email for my blog was too long to display both. With the issuer parameter, Google Authenticator (latest version on iOS) shows the issuer above the TOTP and the accountname below (removing the issuer from the label if it matches the issuer).
From https://code.google.com/p/google-authenticator/wiki/KeyUriFormat#Issuer "We recommend using both issuer label prefix and issuer parameter together to safely support both old and new Google Authenticator versions." I changed the email to user_login before I added the issuer parameter because the label and email for my blog was too long to display both. With the issuer parameter, Google Authenticator (latest version on iOS) shows the issuer above the TOTP and the accountname below (removing the issuer from the label if it matches the issuer).