Mobile GPUs (in laptops ) are always weaker than real graphic cards mate, you can do a comparison between a mobile gtx1660ti vs the real gtx1660ti, you will see that the standalone gtx1660ti is more powerful, also I don't recommend mining with your laptop, a laptop that can have a gtx1660ti is costly I believe
It's roughly same spec with the laptop, I've just checked using Google right now, they are both using Gddr6 memory and the clock speed are near identical, it should hash more than 15mhs, something is wrong, but all the same you will kill your laptop if you use it for mining