Watch this video captured and posted to Instagram.

https://www.instagram.com/p/CHky6Y1pCX2/?utm_source=ig_embed&utm_campaign=embed_video_watch_again

It appears that the practice area collects the balls in the underground bucket???

According to Golf.com, that is pretty much what happens:

One Instagram user, however, who says he lives in Augusta, Ga., commented on the Instagram post and said: “The practice greens have pipes that run to each of them. They will push the balls in the cup and back in the tent someone will press a button and the balls return to the tent.” Seems like a likely explanation.