Explained in slightly more detail here: https://www.reddit.com/r/VALORANT/comments/fxhjgx/crosshair_dot_is_not_in_the_middle_of_my_screen/fmviwwx?utm_source=share&utm_medium=web2x
Basically, make sure your dots and lines are all even numbers or all odd numbers. If you mix even and odd you'll get misaligned elements.