According to the API documentation Method: listSystems should return the following things:
int "id"
string "name"
dateTime.iso8601 "last_checkin" - Last time server successfully checked in
dateTime.iso8601 "created" - Server registration time
dateTime.iso8601 "last_boot" - Last server boot time
int "extra_pkg_count" - Number of packages not belonging to any assigned channel
int "outdated_pkg_count" - Number of out-of-date packages

but instead it returns only the following data:

{'id': 1234, 'name': 'exampleserver', 'outdated_pkg_count': 0, 'last_checkin': <DateTime '20180413T14:30:36' at 7f417dfce860>}

The following are missing: last_boot, created and extra_pkg_count

Am I missing something?