The size of the spot depends on how long the pregnancy has gone, the age of the mother, the fertility of the mother, the health ect, ect. My two Sword females differ greatly, one gives birth to about 20 and the other has 100+ they have different lenghts to their terms and their willingness to spawn, in short it is a craps shoot. The only way to be able to guess is to keep a journal and go from there. It can take several birthings before you you have a clue, so keep a journal as a help aid. This can also help if you have sicknesses.HTH