When I reached 2 billion, the number of money turned into -19 billion.

And apologize for my bad English  grammer.

https://en.wikipedia.org/wiki/Integer_overflow

It's a known bug that will be fixed one day. Basically you are not supposed to be able to earn this much money.

God Damn... played this game on one save for a year... only got to 1.2 billion. Using the stocks and letting my computer run while streaming.