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At one point the calibration will do a testcut to improve the accuracy. It is ok to wait with the router bit and turning on the machine until just before that.
A picture would help, but as a new user you might not be able to do that right away.
To loose bungees can cause a chain jump. To short can snap.
You could manually put the chain on the sprocket in the 2 extreme positions short/long to get a ‘feel’ how short to make the bungees.
Edit: A picture of my first frame 2017
I took the hooks for the bungees out with an additional 2x4 to help align the chain with the sprocket.
It’s worth to look up the top chain inventions here and also the weight vs. bungee arguments.
My ugly solution that is confirmed to work well: Poor man weight chain tensioning