Blonding is when the shot looks thin,watery and light in colour (not white - thats crema); a bit hard to tell from your video but Im guessing around the 40sec mark.
There are no absolutes with blonding; it can occur a different stages depending on the quality of the bean and grind, dose and distribution (ie technique).
Developing a consistent technique is the first thing but difficult as conditions are always changing: beans age, humidity varies, bad hair days, etc..
Te best advice here is practice and patience. If you google espresso blonding you will find a lot of info including youtube vids.