SSD speed

I bought this SSD https://www.newegg.com/Product/Product.aspx?Item=N82E16820156150 about a month ago. I use a very old Gigabyte GA-965P-DS3 with a SATA III PCI-e card for the SSD. But when I check its speed I get around 200 MBps instead of what should be around 500 MBps. Is this due to the PCI-e bandwidth or what?

My parents computer that also is SATA III gets around 200 MBps as well. So something isn't right here.