What the video shows
The clip runs 一 stroke by stroke at writing speed, then repeats the whole character so you copy the rhythm instead of only counting strokes.
Every turn belongs inside a single stroke. If you lift the pen at the corner, the character looks broken even when the order is right.
Turn the video into practice
Watch once without writing, then write along while it plays, then write from memory and compare with the paused frame.
The example word 一天 (yī tiān) is a good place to use it; three passes a day is enough, and the point is not lifting the pen inside the turns.
The mistake to watch
Lifting the pen in the middle of a stroke that should turn. The order can be right while the turns break, and the character still looks loose; keep each turn continuous and the structure holds.
Watching is not practice
A clip shows the motion; the order only sticks when you write it. Practise the character in the app and let the AI check every stroke.