How do i decrease input blocks?

I've only 1 input RCA audio source, hence, I'm looking for only 1 signal input block. But unlike 1 output block, by default i'm getting 8 input blocks.

I'm able to reduce the input blocks to 2. Is it not possible to further reduce the input block by 1? If yes, then how do i do it? Kindly reply.

Thank you.