The effective permissions shown on the previous page are only estimated permissions based on the specified user logging on to this system. The user could access this file or folder through a share, proxy server, or other method and that would change the actual permissions. Also, once the user logs into the system, local policies or group memberships could affect the effective permissions the user has to the file/folder you are inquiring about. Always remember that effective permissions are estimated permissions, not actual permissions.
Effective permissions are the combination of folder and file permissions. The most restrictive permission prevails. For example, if a user has the Everyone group full control and a file read permission, the effective permission is read. However, if the user is a member of several groups that have full, read, and read/execute permissions, the least restrictive permission applies, in this case Full Permission.
Next: Setting NTFS Permissions