Why is textNumberPattern="#E#" invalid?

[Roger L Costello]

Hi Folks,

My input is this exponential number:

        3E2

I have found that these are valid values for textNumberPattern:

        #E0
        0E0

But this is invalid:

        #E#

That seems odd to me. Why is that invalid? After all, both # and 0 mean digit 
(0-9), right?

/Roger