How to change the rng value

I would like to check with you the following code

list_of_rng_seeds = [12, 2, 1];
  num_rng = length(list_of_rng_seeds);
  for rng_usage_idx = 1 : num_rng
    this_seed = list_of_rng_seeds(rng_usage_idx);
    fprintf('Below results are for rng = %d\n', this_seed);
    rng(this_seed);
      unused_rows = 1:6;
      while ~isempty(unused_rows)
        N_UE_rows = 2;
        rows=unused_rows(randsample(length(unused_rows),N_UE_rows))
        [~,idx]=find(ismember(unused_rows,rows))
        unused_rows(idx)=[]
      end
  end

In the code the number of rows for each rng is getting fixed, say for example for rng=1 ,(34) and (12) form groups. I would like to check how to have variable numbers such that (3),(2),and (14) for rng.