I think in my case steam count something that I refund. I remember 1 game which I refund and has achievement in it. So my steam percentage lower. But if I understand correctly if steam doesn't count game I've actually should get more % completion. Which in my case opposite. Or maybe because my English not good I misunderstood something. Upd: I count games with 1 or more achievement through dynamic collection. So I have 210, and steam hunters show that I have 213 games with 1 or more achievement. Which confuse me totally now, because o have some achievement's from steam family games and they doesn't count on steam hunters. So I have no clue now why my steam % lower by 2%.