Google rolls out the ability to have different Voice and Fi numbers on the same account Google has. That might be handy if, for example, you want to use one service for a personal number, and the other for a business number.
The feature addresses a critique of Fi that has existed since the first wave of invitations went out in 2015 for the service.
Previously, you had to port your Voice number to Fi if you wanted to use your Google Voice number on Google Fi, which means you 'd lose the ability to use it with Voice.
You will be able to forward calls from Google Voice to your Google Fi number when this new feature is rolled out for you, though.
According to Google the feature should be fully rolled out by June 25th.