To learn more about phantom stocks, read our explainer here.
Go to Cap Table (left side nav) → Share Class → Select Add a Share Class
For Section 1, select Exclude from Fully Diluted
Fill out Section 2 and 3, then select Save & Continue at the bottom of the page.
Done! Now anytime you apply this share class to a security, you'll still be able to keep track of the share amount without affecting the fully diluted amount.