@Calinou So i have to change the godot code to make it in grams or smthing. How do I change the code?
Do i need to download the c++ module, also why isnt this a part of godot's main build?

So i have to change the godot code to make it in grams or smthing.

We shouldn't change the unit in which mass is specified, as doing so will break compatibility with existing projects. It's still kilograms in this pull request, but you can now specify the weight down to the nearest 0.001 unit.

How do I change the code? Do i need to download the c++ module,

See Compiling in the documentation.

also why isnt this a part of godot's main build?

This is a pull request, so it isn't merged in Godot yet. Once it's merged, you will need to compile the master branch from source as linked above, or wait for the next stable release to come out.

Thanks!