Don't panic! The numbers 475 and 477 don't refer to the plan names--Like Blue Precision 205 or 206. These are group numbers used to identify the HMO medical group number. 475 and 477 refer to Northwestern's medical group number that you will select either on your application or after you sign up. You can choose any Blue Precision HMO plan, bronze, silver, etc and have access the to the Blue Precision hospital network that includes these medical groups.
Check out this article for more information about accessing Northwestern Hospital: