Some error checking algorithms are actually "forward error correcting", that is, they can be used to correct a limited number of bit errors in a message after it has been received. Hamming codes are an interesting example, where several extra check bits are sent, like 3 extra bits for each set of 4 message bits. This can correct all single bit errors and detect 2 bit errors, but not correct them. See Hamming code - Wikipedia
It is conceivable that this is one of those algorithms, but that is certainly not obvious and in any case, I doubt more than one bit in the entire message could be corrected using a single byte "checksum" like this one.