Exactly! You got it. All currency redeemed, or bought back, by the CBI is no longer considered in circulation.
Remember the Kuwait story and their dinar. Kuwait only had about 400 million dinar in circulation when Saddam invaded them. He broke into the Central Bank of Kuwait and stole billions that they had stockpiled for future use. That’s why the value of the Kuwaiti dinar plunged on the street, he basically dumped billions of illegal Kuwaiti dinar into circulation on top of the small legitimate amount. That currency in Central Bank is not part of currency in circulation.