The number refers to the scene release number for the North American (USA) version of Pokémon HeartGold Version
If you want a hassle-free way to replay HeartGold and don’t mind paying a few bucks for someone else to curate some themed extras, this is fine. But for most people, you’re better off getting the ROM for free (from a safe, legal source if you own the original cart) and grabbing fan-made content separately. The lifestyle angle is a nice idea, but underdelivered. 4780 heartgold download hot
: You can find rare items like the Exp. Share by trading a Red Scale to Mr. Pokémon or find the Never-Melt Ice on the Ice Path. The number refers to the scene release number