The solenoid is the primary coil while the green wire is the secondary.
The video shows clearly how the secondary voltage is proportional to the number of turns in the secondary coil.
Since each additional turn increases the secondary voltage by about 0.064 V, and assuming that the primary coil is 230 V, the number seem to be suggest that the primary coil has about 3600 turns. It does not look like the primary coil has that many turns. So probably there is a lot of flux leakage.