The SenderID that is present in the initialization example is a gcm sender id that is given to you by google. It should also be present when you install the plugin
ionic plugin add phonegap-plugin-push --variable SENDER_ID="XXXXXXX"
If you wish to add additional data to your push notifications look in to this link explaining how to add more typings https://github.com/phonegap/phonegap-plugin-push/blob/master/docs/TYPESCRIPT.md