You can go to the Campaigns tab, and then click on Keys to open up the page where you'll see this information.
To see remaining keys, go to the Campaigns tab on the top of the screen, next to the Home tab. Then go to the Keys section.
Under Active Campaigns, you will see the different ongoing Campaigns you have as well as a key icon. This will show you the amount of keys left out of the total amount in added to the keyset.