select
len(substring(story_nvar,1,10000)) [Length of SUBSTRING(NVARCHAR(MAX))],
len(substring(story_nvar,1,10000) + cast(number_stored_as_int as nvarchar(1))) [Length of SUBSTRING(NVARCHAR(MAX)) + 1 NVARCHAR CHAR]
from dbo.twain

select
len(substring(story_text,1,10000)) [Length of SUBSTRING(TEXT)],
len(substring(story_text,1,10000) + '1') [Length of SUBSTRING(TEXT) + 1 CHAR],
len(substring(story_text,1,10000) + cast(number_stored_as_int as nvarchar(1))) [Length of SUBSTRING(TEXT) + 1 INT cast as NVARCHAR(1)],
len(substring(story_text,1,10000) + cast(number_stored_as_int as nvarchar(MAX))) [Length of SUBSTRING(TEXT) + 1 INT cast as NVARCHAR(MAX)]
from dbo.twain

select
len(substring(cast(story_text as nvarchar(max)),1,10000)) [Length of SUBSTRING(TEXT)],
len(substring(cast(story_text as nvarchar(max)),1,10000) + '1') [Length of SUBSTRING(TEXT) + 1 CHAR],
len(substring(cast(story_text as nvarchar(max)),1,10000) + cast(number_stored_as_int as nvarchar(1))) [Length of SUBSTRING(TEXT) + 1 INT cast as NVARCHAR(1)],
len(substring(cast(story_text as nvarchar(max)),1,10000) + cast(number_stored_as_int as nvarchar(MAX))) [Length of SUBSTRING(TEXT) + 1 INT cast as NVARCHAR(MAX)]
from dbo.twain