First off, you are showcasing a totally artificial scenario where you have added hundreds of millions to your treasury in worldbuilder.top left bar still overflows.
If you had achieved that amount without using the worldbuidler the value showed in the top left corner would have been:
240M 877334 - 9921134
I think I'll change it so that when you have 1 million or more gold, then only the million part will be shown followed by a e.g 401 K,
So the amount shown in your screenshot would then become be:
240M 877K - 9921134
I might even change it so that it would show like this:
240M 877K - 9M 21K
Then, if you want to know how many hundreds you have above the millions and thousands you will have to move the mouse cursor over the treasury chest to see a detailed treasury content.