The current best esimate of the age of the universe is 13.7 billion years. See Table 7, Cosmological Parameter Summary, p. 45, of the linked pdf. There, the age is quoted as t0 = 13.720.12 Gyr, to be precise. The Gamma Ray Burst occured 12.2 billion years ago (because the burster is 12.2 billion light years distant). That is only 1.5 billion years after the big bang. And that makes sense, because these huge objects can’t long endure.