If you had used
VD.A(B, A), the result would be 0.83. With VDA, no effect is 0.50 and 0 or 1 is complete stochastic dominance of one group over the other. This can be a little disconcerting at first, but it makes a lot of sense for this statistic. VDA is the probability that an observation in one group will be larger than an observation in the other group. So the result of
VD.A(A, B) is equal to
1 - VD.A(B, A).
It may be helpful to compare this to Cliff's delta, which is a linear transformation of VDA, where 0 is no effect, and -1 or 1 is complete stochastic dominance.