Hi! Great question. The dot product looks at the projection (or you could think of it like a shadow on the other vector. The value of the dot product is just a value and does not have direction and this is simply a scalar value. If two vector are parallel, to calculate the projection of one onto the other, you can see that the value is the same as the magnitude of the vector. The dot product is:
magnitude(vector 1)*magnitude (vector 2)* Cos (0). Cos(0) is just 1. Hopefully this helps! Best wishes!