IV Calculator question

The IV calculator shows you your level 40 stats, its not possible to have a character with an uneven amount of positive and negative stats.
1 high stat, 3 middle stats, 1 low stat
2 high stats, 1 middle stat, 2 low stats
5 middle stats
Those are the only options. Depending on the star of the unit and what unit it is, usually there is about 3 points between each rank. So for the typical 5 star unit the stat can range from -3 to +3, or 27 to 33.