After investigating DB performance we've come to a conclusion that this index would be useful to be added in ADAM DB:
CREATE NONCLUSTERED INDEX [<Name of Missing Index, sysname,>]
ON [dbo].[tblLOG] ([Severity],[LoggedOn])
Adam support did allow us to add the index into our client's DB and suggested feature request to be made for this.
Customer support service by UserEcho