A vector specifying the number and size of the first dimension of regular input ports indexed from top to bottom of the block. If no input port exist in==[]. The size can be negative, equal to zero or positive :
If a size is less than zero, the compiler will try to find the appropriate size.
If a size is equal to zero, the compiler will affect this dimension by added all positive size
found in that vector
If a size is greater than zero, then the size is explicitly given.
This is explained @ https://help.scilab.org/docs/6.1.0/en_US/scicos_model.html :
in
A vector specifying the number and size of the first dimension of regular input ports indexed from top to bottom of the block. If no input port exist in==[]. The size can be negative, equal to zero or positive :