So I thought about my previous comment and realized how wrong part of it was you shouldn't need to defrag its and ssd.. and from the info I've seen on your ssd its rated at 540MB/s for Sequential Read and 520MB/s for Sequential Write . But that's under ideal conditions. Just try rebooting then testing and stop as many apps as you can before you test. sorry about my bit of bad advise up there
Actually 188Mb/s is pretty respectable, does seem somewhat slow for an ssd though depending on the brand and what generation it is. But a couple things you can do to help the score out are defrag your hdd then completely reboot your system and rerun the test first thing after you reboot.