A positive value is only meaningful if the surface is anchored to one edge or an edge and both perpendicular edges. If the surface is not anchored, anchored to only two perpendicular edges (a corner), anchored to only two parallel edges or anchored to all edges, a positive value will be treated the same as zero.
This PR adds the opposite anchor (RIGHT) to fulfil this condition.
Quoting the spec:
This PR adds the opposite anchor (RIGHT) to fulfil this condition.