In simulink, Why does output datatype does not match to my settings?

Hello, everyone. I am using Xilinx System generator in the environment of Simulink. As you can see, I want to use a parallel to serial block to convert input to boolean output. My settings are showing in the following figure. As there is no boolean output type I choose 1 "Number of bits".But you can see the output type tend to be double rather than boolean or single. I am wondering the reasons. Anyone can help me?