What does Genesis 48:20 mean?

That day, Jacob blessed them and said, 'Israel will use your names when they bless people. They’ll say, “May God make you like Ephraim and Manasseh.”' He put Ephraim ahead of Manasseh. Genesis 48:20 - Modern Text Bible

(Jacob sets Ephraim as the example for future blessings, reversing the usual order and making it a tradition.)