Boys 5/6 Medium Not Normal Boys Medium

I bought a boys Medium as listed and turns out you sent me a boys size 5/6 M. I thought boys, just like the girls chart was a size 10/12; normally if it is the smaller 5/6 it denotes 5/6 not just boys Medium that usually indicates the larger 10/12 size. Want a replacement but think it’s the same smaller size and can’t tell.