The bracelet in the video is a magnetic, flat, bracelet and the advise is based on this type of bracelet.
When buying a Crystal or Pearl bracelet the actual size you require depends on the size of the beads.
The larger the beads the more additional length you have to add for the bracelet to feel comfortable.
A bracelet made with 10mm beads will have to be 2.5 – 3cm longer than the measured size of your wrist.
A bracelet made with 4-5mm beads will need an addition of 1-1.5cm.
These values are just guides as, in the end, it depends on how you feel wearing the bracelet.
Some are more comfortable with a loose fit whereas others prefer a bracelet to be more tightly fit.
If you want a loose fit, add in another 1-2 cm
Just remember, if you order a bracelet with the same size as the measurement of your wrist, it will probably be too short.