Within the archive of Salesforce's community trailblazer pages lives a mythical article covering the "Greatest Formula Ever Written", the Power of 1. Once the steps have been followed to create and configure this field for an object, every existing record of that Object will simply have the number 1 on it, no matter how many hundreds, thousands, millions, etc. of them you have on your SFDC org, and every record that is created after that for as long as you have your SFDC org living. While this doesn't sound so glamorous, the Power of 1 (Po1) field helps fill a gap in the way SFDC summarizes record counts while reporting. More information on the benefits of this field outside of Marketo Measure and detailed set-up steps can be found here.