I am 5'-10" with an 88" ceiling height. I have the same question. Spoke with Schwinn customer service but they couldn't help. Suggested I go to a store and try it out and measure how high my head goes!
I am surprised at how hard it is to get this type of info. Surely lots of people want to put these machines in their basements which might have relatively low ceilings.
I got an answer from Vision Fitness that makes sense to me but you'll need to know the mid-height pedal measurement (average of lowest and highest measurements). Add the mid-height measurement to your height and add a few inches for a safety zone. You are never actually as high as the highest pedal position when you're working out, but you definitely go higher than the "step-up height."
I am shocked that Schwinn could not help you with this.