Why is this string considered length one?

Why is '15' a string of length one?

>> datestamp = '1991-6-15'

datestamp =

1991-6-15

>> a = textscan(datestamp,'%4s %2s %2s','Delimiter','-');
>> length(a{3})

ans =

       1

>> a{3}

ans = 

      '15'

I'm trying to get the length of the string. Sometimes letters will be used, so converting to numbers is not an option.

Why is '15' a string of length one?

[cypher]

ANSWER:

a{3} is a cell array of one cell

a{3}{1} is a cell of one string

length( a{3}{1} ) is 2

Answer 1

[cypher]

ANSWER:

a{3} is a cell array of one cell

a{3}{1} is a cell of one string

length( a{3}{1} ) is 2