Numb Nut
The folded arm over the knee is a typical 'SITTING' FT position.
There is NO sitting allowed in HFT.
Another favorite FT position is to have the left hand (RH shooters) resting on the front of the knee and the gun resting on the top of the hand. This is not allowed in HFT and as such the hand has to be forward of the knee.
HTH