Unexpected results, Smart Collections

There are 203 image files in the RG folder of my HD; a number that is confirmed by the OS file manager.

I imported then all and gave them the keyword: "RG Proj." When I select/All the KW window shows "RG Proj" with no asterisk, meaning all the selected images have that KW.

But here's the rub; when I run my "RG Proj" Smart Collection, with the filer: "Contains Words/RG Proj I get 199 images.

What could account for this mispatch?