Add a clarification to a comment

Signed-off-by: Gavin D. Howard <[email protected]>

src/num.c

@@ -1956,6 +1956,9 @@ bc_num_d(BcNum* a, BcNum* b, BcNum* restrict c, size_t scale)
  // actual algorithm easier to understand because it can assume a lot of
  // things. Thus, you should view all of this setup code as establishing
  // assumptions for bc_num_d_long(), where the actual division happens.
+ //
+ // But in short, this setup makes it so bc_num_d_long() can pretend the
+ // numbers are integers.
  if (cpardx == cpa.len) cpa.len = bc_num_nonZeroLen(&cpa);
  if (BC_NUM_RDX_VAL_NP(cpb) == cpb.len) cpb.len = bc_num_nonZeroLen(&cpb);
  cpb.scale = 0;