Google Document AI value types Money vs Currency

I noticed this when I was working on a Schema for a custom processor it seems that there are two different options for money I'm not sure what the difference is. or to put it another way when should I use "Money" and when should i use "Currency" ?

As I replicate your question with a sample invoice file, here are my observations.

Currency data type identifies the type of monetary system. For example in the image below “$” is captured as USD. And for the Money data type it captures the monetary value beside currency.

You can use “Money” when you need to capture numerical monetary value while “Currency” to identify the ISO code of the monetary system.