They all need to be drawn in the same direction of the demo. If I draw them in the opposite direction ( example the circle instead of counter-clockwise, I draw it clockwise ), another shape is recognised:
When I was a teenager playing Dr Kawashima's Brain Training on DS, I had to completely change how I drew my 9s in order to get it to recognise them (it turned out I started in the wrong place for it to recognise the number).
I only played that game for a month or two, but it stuck with me and now more than a decade later I still draw my 9s differently.
Well, it's not magic. It probably recognizes direction of strokes. I imagine that you can start from scratch and train both directions to be valid, but then you will find more mismatches.
Triangle -> Delete / Caret
X -> Delete
Rectangle -> Caret
Circle -> Caret
Check -> Right square bracket / Arrow
Caret -> V
Zig-zag -> Zig-zag
Arrow -> V
Left square bracket -> Right square bracket
Right square bracket -> Left square bracket
V -> Caret
Delete -> X
Left curly bracket -> Right curly bracket
Right curly bracket -> Left curly bracket
Star -> Left curly bracket / Delete
Pigtail -> Delete