Matrix downsampling

Mattebass's icon

Hello, I'm working trough audio applications of Jitter, and I was wondering about data communicating between two jitter matrix with different dimensions. On documentation is said that If I would send a bigger matrix in a little one, data are discarded due to no space for complete copying. My question is about the process of discarding: only the first data are retained? only one sample per vector?
Does anyone has an idea

Thanks

Matteo