Here is a gentle reminder courtesy of Ravi Nishant https://www.linkedin.com/in/ravi-nishant-b83723259/
This is what I know for sure. If you check, you will realize that you will never have 100% of spend under management. You should then look at all the other spend buckets and determine what has been ignored for a while. I would expect that you can easily find $2M, depending on the size of your organization. I use the 10% rule to establish my minimum savings goal.