“as he went up Rosh Chodash Elul and descended on the Yon Kippur with the second luchos when the sin was forgiven”
With all information but the bottom line is in truth klal yisroels was never fully forgiven for the son of the Aigel which is also why Hashem did not give up the new luchos but this time it was man made by Moshe Rabbeinu our leader