Sam Mitrovic explains the scam:
Recently I received a notification to approve a Gmail account recovery attempt.
The request originated from the United States.
I denied the request and about 40 minutes later received a missed call. The missed call showed caller ID as Google Sydney.
I soon forgot about this.
*****
Exactly a week later, more or less exactly the same time, I received another notification to approve my Gmail account recovery again from the United States.
You guessed it – about 40 minutes later I receive a call which I pick up this time.
Read more at SamMitrovic.com.
h/t, Davey Winder