Is 30 mins exercise bad?

So... I can manage 30 mins exercise on a step aerobics stepper and my boyfriend said I'm lazy and should do 1hrs exercise. I told him it's easier to manage 1hr doing different exercises not just on a stepper as that's hard work.

Am I really in poor shape physically if I can only manage 30 mins a day 4 times a week on a stepper?
Is 30 mins exercise bad?
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