Grade listing question

Just checked my coins listed against grades, and noticed that I have 1 coin listed as N/A.
What does this mean?
Secondary question. How do I find which coin it is, so I can sort it?

I have done this by using the export to XLS feature from My coins page.

Downloaded xls spreadsheet as recommended, but it does not show a N/A in that listing.
This is a copy of what I see on my screen.


VG 3
F 40
VF 373
XF 8257
AU 17
UNC 6699
N/A 1

The total is correct, so something is wrong somewhere

Can you see in the grade field of the spreadsheet any blank value?

Some of my swap coin I do not fill the grade, so they shows as blank on the XLS.

Yes, I noticed the blank area under the grade column, but these are my swap coins, so no grade is ever listed.
The line within a coin, allows you to add coins in different grades, but only an amount of coins in the swap box, so completely baffled as to why I have a N/A.