why I can not see partition schema be modified ?

Dear :

   I can not see the a partition schema use the next group ?

   I have an partiton schema  script is:

CREATE PARTITION SCHEME [ps_OneMillion_LeftRange] AS PARTITION [pf_OneMillion_LeftRange] TO ([PRIMARY], [FG_1], [FG_2], [FG_3], [FG_N])

   then I create a new filegroup and add a file in it.

alter database sample_DB add filegroup FG_N1;

alter database sample_DB add file (
name = FG_N1_DataFile,
filename = "D:\Sample_DB\FG_N1_DataFile.ndf",
size = 10M,
maxsize = unlimited,
filegrowth = 1M)
to filegroup FG_N1;

  Then I try to make the partition schema to use the bnew file group:

alter PARTITION SCHEME ps_OneMillion_LeftRange NEXT USED FG_N1;

 But when right click on this Sample_DB and select storage and find the partition schema and get the script by create to.

The partition script is the same.

CREATE PARTITION SCHEME [ps_OneMillion_LeftRange] AS PARTITION [pf_OneMillion_LeftRange] TO ([PRIMARY], [FG_1], [FG_2], [FG_3], [FG_N])

not I expect 

CREATE PARTITION SCHEME [ps_OneMillion_LeftRange] AS PARTITION [pf_OneMillion_LeftRange] TO ([PRIMARY], [FG_1], [FG_2], [FG_3], [FG_N],[FG_N1])

Why  and doest alter schema not OK ?