Here's a list of standard ports you should see at least once. You shouldn't remember them (the exam will not test you on that), but you should be able to differentiate between an Important (HTTPS - port 443) and a database port (PostgreSQL - port 5432) 

Important ports:

• FTP: 21

• SSH: 22

• SFTP: 22 (same as SSH)

• HTTP: 80

• HTTPS: 443

vs RDS Databases ports:

• PostgreSQL: 5432

• MySQL: 3306

• Oracle RDS: 1521

• MSSQL Server: 1433

• MariaDB: 3306 (same as MySQL)

• Aurora: 5432 (if PostgreSQL compatible) or 3306 (if MySQL compatible)

Don't stress out on remember those, just read that list once today and once before going into the exam and you should be all set :)

Remember, you should just be able to differentiate an "Important Port" vs an "RDS database Port".