This will only work if you have the number of tracks actually in the number of tracks field or alternatively in the Total tracks field. You will probably find them to be empty if you look at the relevant tags - hence all of your albums have a value less than 7.
If you want to fill the total tracks (you can't change number of tracks) you can set up a smartlist by clicking on the import/export button and then pasting this into the box
[=save(0,var_number_of_tracks[album artist (auto)][album][file type][bit depth])1]=1 [=save(math(1+load(var_number_of_tracks[album artist (auto)][album][file type][bit depth])),var_number_of_tracks[album artist (auto)][album][file type][bit depth])1]=1 [Media Type]=[Audio] ~sort=[Artist],[Album],[Name]-d,[Media Type],[Album Artist (auto)],[Disc #],[Track #]
then select your files and paste this into the Total tracks column
=load(var_number_of_tracks[album artist (auto)][album][file type][bit depth])
This should fill your album's Total Tracks field with the number of tracks for each album and then you can write a smartlist selecting for Total Tracks is less than or equal to 7.
Hope this helps.