I have the same SSD running my OS. I've have just run two CrystalDiskMark benchmarks with differing loads for you + There are two from Samsung Magician from back when I had just installed it and another one from just now. As you can see I'm getting higher marks than you across the board. I have little knowledge on how you can better this, but here are two possible explanations.
Make sure it's connected to a SATA 3 (6Gb/s) port?
Is the SDD filled to the brim without Over Provisioning? (Use Samsung Magician to reserve Over Provisioning space which is used for moving stuff around internally in the SSD)
Samsung Magician from when the SSD was just installed.
Sequential Read - 551 MB/s (Up to 540) Sequential Write - 523 MB/s (Up to 520) Random Read (IOPS) - 99024 (Up to 97000) Random Write (IOPS) - 86525 (Up to 88000)
(Yes it's the correct numbers, it does score above the limit on all but the last one)
Samsung Magician Benchmarks from just now.
Sequential Read - 552 MB/s (Up to 540) Sequential Write - 468 MB/s (Up to 520) Random Read (IOPS) - 97445 (Up to 97000) Random Write (IOPS) - 75368 (Up to 88000)
So it seems the write speeds have suffered a bit since the first benchmark.