You can organize your guests in groups. This way, you can easily keep track of the number of guests you invited according to their group as well as those who have confirmed. 

To create a group, just click "Add Group".

You can then create a name for your group.
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You can choose from the color selection if you want to change the color of your group. After that, you can either click save or if you want to add more, just click "Save and add more" from the options.

You can now effortlessly check attendees or the people who needs follow up. 

Go here to learn more about how to edit and delete groups.