MR24HPC1 - checksum calculation

I have looked at the user manual and the demo to send data to sensor. But I do not understand how you arrive at a checksum of 0xB5 from 0x53, 0x59, 0x08, 0x00, 0x00, 0x01, 0x00 (the close_buff command in the demo 3 24GHz mmWave Human Static Presence Lite | Seeed Studio Wiki). Is there some documentation/examples of adjusting the settings on the sensor?

I’ll give you an example of the data frame you provided:
0x53 0x59 0x08 0x00 0x00 0x01 0x00
They are hexadecimal numbers, so you need to open up your calculator and adjust it to calculate hexadecimal addition, which you will get:
So the checksum is 0xB5.
It should be noted that the “0x” written here means hexadecimal number and is an artificial notation.