SN550 1T 4k random write test result very slow

Hi, I tested my new SN550 1T with crystaldiskmark and AS-SSD-benchmark, both results are not as expected or advertised. Random 4k write speed is much slower, about half of the advertised speed.

I am wondering if i received a faulty product or i need to do something about software/driver in windows 10, e.g. the HMB thingy.

Anyone has the same issue or can help? cheers!