You should consider the bnn.lis file.
There energy deposition density values [GeV/cm^3 per primary proton] are listed row-by-row, with no explicit info on x/y/z. The first value refers to the first bin of the mesh (i=1,j=1,k=1), where i,j,k are the bin index in x/y/z. Then i is looping first, j second and k last. In your case, the first 200 values (in the first 20 rows) refer to j=k=1 (-100<y,z<-99), with i running from 1 (-100<x<-99) to 200 (99<x<100), and so forth.
Note that on the transverse x/y dimensions, one should better ask for an odd number of bins, in order to get a central bin around x=y=0 and so avoid to underestimate the maximum energy deposition inside the beam core.