Several of these stars are variable or have companions, so their brightness may shift. Ranking in this table is thus variable, especially towards the bottom. You may see slightly different ordering in similar tables elsewhere.
Most stars are in such systems, usually binaries.
The individual stars in the multiple, however, may not be bright enough to make this list. In fact, Alpha Centaurus B, at visual magnitude 1.33 is the only star that would merit a separate entry in this abbreviated list. The brightest magnitudes are the largest negative numbers. As measurements improved, it was found that some 1's were brighter than the others, hence numbers smaller than 1, eventually running into negative numbers. The scale is logarithmic, and each increase in 5 magnitudes corresponds to a decrease in brightness by a factor 100.