it's somewhere explained but.
You have to install the shelly as shutter with two bulbs and two switches (as end positions)
Than you have to measure the working time from open to close and from close to open.
Now you start the calibration, when you have the working time you take off the first lamp.
When than the other is on you turn the first on back, and than you have to turn off the second.
That you do all the time and at one point you finish the calibration.
Wiring is than,
L=L
N=N
O = lamp - switch - n
(By both the same)