kalman filter input removal

I am forcefully adding 28 inputs so i can get the kalman filter to run( my input is 28 columns so i need 28 inputs) , i would like to remove the extra 25 inputs(i need the original three only for the result) from my input; i saw a the code given in mathwork documentation to remove ye input by using the below syntax

SimModel = SimModel([1 3],[1 2 3]); % Delete yv from I/O list

i cant understand what and how is the syntax taking out yv from the i/o list and i need help to understand it

if i can understand the syntax i can use it for my model

Thanks in advance