A Stanley 500-Amp Battery Jump Starter cannot be used to charge a car battery, it's meant for boosting a dead battery. The battery status sign shows the level of charge of the internal battery whereby it has three colors red, yellow and green.
You say it's a "jump starter." A jump starter and a charger are not the same thing. The jump starter may though be able to charge its OWN internal battery. Do you have the manual that came with the jump starter?