The Preferred name field in account settings should contain only a first name or given name, not a full name. 15Five automatically appends your last name from the Last name field when displaying your name throughout the platform.
If you enter a full name (e.g., "Alex Smith") in the Preferred name field and your last name is already "Smith," your display name will appear as "Alex Smith Smith" across 15Five.
To fix this, go to Settings > My settings > My Information and update the Preferred name field to contain only your preferred first name (e.g., "Alex").