What does the Memory Box on Performance Stats actually record?

So I've been preparing a game for release, and I plan on having a massive world and many assets in my game.

Anywho, as I was roaming around the Robloxiverse, I've also been toying with the Performance Stats feature, specifically Memory.

Now, if you've ever seen the Performance Stats they note that the target memory is 200 MB, and a green color is safe, yellow is borderline, and orange is considered excessive. This is clear.

However, many games I have tested with this feature are always in the orange range. For example, MeepCity fluctuates around 300-400 MB. Another, JailBreak, remains always over 500-600 MB.

JailBreak is a considerably large game, I agree, but MeepCity doesn't seem to deserve that high of a memory since most parts are hidden from the player at any time. I do know that MeepCity stores many IntValues in its ReplicatedStorage in order to remove and clone back the "worlds".

I suppose the memory takes into account these IntValues, maybe some tables from Lua code, and all the visible parts in Workspace. That's just my guess, and I would love some insight from more experienced Robloxians.

What exactly does the Memory stat measure? And how much is considered too much memory? What would be the best way to effectively manage memory in large games?