...
Use the Validate expression button to ensure you are using a correct expression.
...
Fields value security
The value of a field can be restricted so only a certain individual or group of individuals can view or edit it. These restrictions are subjected to the permissions selected in the Permission Scheme of each project, see Manage permissions section.
Editors of the field values
In this dropdown you can select the Jira user group that will be able to edit this field. Additionally, you can choose from:
By default, editors will always have the possibility to view too.
You won’t see this dropdown in formula fields as they aren’t editable.
...
Viewers of the field values
In this dropdown you can select the Jira user group that will be able to view this field. Additionally, you can choose from:
Public
Any logged in user
Only editors (not available on formula fields)
Nobody (only for formula fields)
...