Fast bin is using  "size_t thissize = chunksize (p);".  
Using r->size directly gives wrong total and avail size data.

       if (r != NULL)
          while (r != bin)
            {
              ++sizes[NFASTBINS - 1 + i].count;
              sizes[NFASTBINS - 1 + i].total += r->size;
              sizes[NFASTBINS - 1 + i].from
                = MIN (sizes[NFASTBINS - 1 + i].from, r->size);
              sizes[NFASTBINS - 1 + i].to = MAX (sizes[NFASTBINS - 1 + i].to,
                                                 r->size);

              r = r->fd;
            }