I want to break down the components:
1. The song is non existing on streaming chart, so I believe major of the point is from BGM and download.
2. I am not sure how big the BGM chart effect, but I dont think it has much impact to get this many points.
3. Download: this one a very tricky one, I dont think Daniel fanbase is any bigger then BTS or IU. I believe if download can drive the Gaon points this much, Korean Army already done that long before. Even Life goes on for the first 2 weeks (10 days tracking) combine just barely around this number, even LGO had better streaming number.
So I think there will be 2 options:
A. Fans bought digital downloads on all the platforms that counted towards chart. But I dont think Army has not done this, consider how huge the army is.
B. Unlimited download from a strange source which allow fan buy multiple copies of the same song. Something BTS did for their web store. But again, if BTS fans know about it, they already mass bought before.
What do you think?