First of all, I don't know what the arrow through the crystal means in that picture. Is it the direction that the thumb should be directed when using the LHS method?

Also, I learned that the line from finish point to start point is Burgersvector, but the one I got and the one presented in the picture show a different direction. What's the problem?

I$\text{'}$m so confused about how to get the burger vector in screw dislocation