Does Glibness replace the number on the die with 15?

@JeremyECrawford Does Glibness replace the number on the die with 15, or replace the number on the die + modifier + proficiency with 15?

— _ (@MoronsRus) May 30, 2017

Glibness can replace the number rolled with 15. You don't roll your ability modifier, proficiency bonus, etc. They're still added. #DnD https://t.co/Et7j3GEk67

— Jeremy Crawford (@JeremyECrawford) May 30, 2017