Companies are supposed to (and essentially always do) issue conservative estimates for performance. Therefore, since they said 20mm, we know that they actually expected 21 or 22 million. If they fall short of 20mm units, that will be seen as a significant miss by anyone that cares about the financial performance of Nintendo.
Recently we have seen Sony basically under project for PS4 every single year (sometimes over than 2M).
Also we have seem Nintendo over project on 3DS and WiiU, but get close U/O on Switch. If they get under 2M of projection while being conservative that can impact them negatively.
duduspace11 "Well, since we are estimating costs, Pokemon Red/Blue did cost Nintendo about $50m to make back in 1996"
Mr Puggsly: "Hehe, I said good profit. You said big profit. Frankly, not losing money is what I meant by good. Don't get hung up on semantics"