Issue on rights for Custom fields

I had a look at the database (oracle in my case)
I found strange rights like that :
RIGHTNAME

AdminCustomField
AdminCustomFields
AssignCustomFields
ModifyCustomField
SeeCustomField
ShowCustomField

There is some instance of AdminCustomField (without s) that seems strange ?
Also I would like to understand what is the difference between
ModifyCustomField and AssignCustomFields
Thanks for your quick feedback
Do I need to replace some of them by a global replace ? in Database ?
Jean Marc

Jean-Marc Lambert
EMEA MIS/IT Operations Manager
Axalto
6, rue de la Verrerie
92 Meudon
Tel : +3315501 5484 (Meudon Office 15Apr06)
+33611765664 (GSM)