You were unable to explain the unit of WHAT is BTC.
I've illustrated the essence of a Bitcoin unit. It signifies a numerical value within a distributed, resilient, and incorruptible database. It doesn't denote the quantity of a tangible asset, much like electronic poker chips don't signify any physical object, yet they possess specific characteristics that make them valuable.
As for ABC, how do you know that the item that Bob has is a coin? How do you know that 10 ABC means 10 coins if you cannot show anything in the quantity of 10?
If I create an online game and grant you 10 "e-diamonds," there's no physical item I can present to depict these diamonds. They exist solely within the confines of my game's rules. Should you trust me, these e-diamonds can attain value and serve as a form of currency.
Only SOMETHING actual can have a supply. You mentioned numbers. Numbers are mathematical abstractions and they're infinite. There's no such thing as a supply of numbers. Only SOMETHING actual, something that can satisfy human needs can have a supply. And in the Bitcoin system there's nothing ACTUAL that you can name or show. BTC is indeed the unit of nothing. An empty and invisible container. Thanks for proving my point.
If that were the case, then send 1 million bitcoins to this address: bc1q0u2tencdlkzeungrj7zsswl62nlxgucghhanwe. Since they're merely abstract figures in a database, it shouldn't pose much difficulty for you to generate them out of nothing, correct?