window roll up's

hi i installed a window roll up that works with the keyless entry system.i encountered a problem where when i connected  the (-) input wire to roll the widow's up to the (-) lock wire of the keyless entry system,the window's went up when the doors unlocked.so i used the (-) unlock wire,it worked perfect.now my question is why this worked this way.by the way it was a nissan sentra.