Question: Problem with the summation of space and space-time coordinates in the "Physics" package

I have the following problem, I want to define my own covariant derivative. This mixes my gauge fields with the Pauli matrices. My Setup() looks like this:   

restart;
with(Physics);
Setup(spacetimeindices = greek, spaceindices = lowercaselatin_ah);
Setup(signature = `-++ +`);
Setup(coordinates = spherical);
 

And this is my covariant derivative: 

Define(D[mu] = d_[mu] + 1/2*ig*Psigma[a]*A[mu, a])

If I output the tensor, MAPLE should automatically perform a summation over the spatial indices a, right? It looks like this in my case: 

I find the indexing a bit strange. When I look at the first entry, for example. Why does a in A[mu,a] go from 1-3 and the a of Psigma[a] from 2-4? They should both be spatial indices, right? Can I change the indexing in Setup() or am I doing something wrong here?