Congratulations and no problem. Students come in at every level imaginable.
Do your own thing and don’t worry about the other people.
They want you to come in ready for Calc 1. They are nationally known for their Calc curriculum (read : hard ?).
Michigan told you with your acceptance they think you will do well. Now the fun begins…
Email your department and see if you can place out. I don’t think so. Freshman year for many is not a cake walk especially in your field. It’s not an easy school but well worth it if your willing to put in the work. Work/Reward is great at Michigan.