The end point for a distillation fraction is the temperature at which 100% of the fraction has evaporated when distilled.

This means it is also in theory the cut point between the fraction and the next heavier fraction being distilled, and the initial boiling point of that heavier fraction.

However, in reality the true end point of a fraction is typically higher than the true initial boiling point of the next highest fraction (they over lap) because they are complex mixtures of different hydrocarbons. Consequently, the refiners in practice split the difference and define an "effective" end point that is in between and therefore lower than the true end point.