Hi Murat,
Looks like this block in the shared block diagram is 'Dot Product' block.
The Dot Product block generates the dot product of the input vectors. The scalar output, y, is equal to the MATLAB operation
where u1 and u2 represent the input vectors. The inputs can be vectors, column vectors (single-column matrices), or scalars. If both inputs are vectors or column vectors, they must be the same length. If u1 and u2 are both column vectors, the block outputs the equivalent of the MATLAB expression u1'*u2.
Refer to the following reference to know more about 'Dot Product' block:
I hope this helps.