I don't have RSLogix 5, but I do have RSLogix 500, which is very similar.
To verify my information, I clicked the Help button in that dialog box and followed a link there to "Data File dialog box properties". It has a table that explains what each letter means. You may have to follow a different path to get there in RSLogix 5.
Basically, the "W" means that it's used as a "word", so the code somewhere is looking at B3:22 instead of just B3:22/0. The "F" means it's used as a "file" address in instructions like FLL or COP.