read bytes from ext3 linux filesystem

Question

I have a project for a class in which we're supposed to read each block into a buffer and compare the bytes to look for a mp3 file signature.

We are supposed to start with a zeroed out drive (I had an ext3 filesystem which I zeroed out using dd if=/dev/zero of=/dev/sdc1) and print out that there are no matching bytes to the file signature.

Currently, using the code shown below:

int main (int argc, char* argv[]) {
    printf("argc : %d \nargv %s \n", argc, argv[1]);
    ReadDataBlockTest(argv[1]);

    return 0;
}

void ReadDataBlockTest(char* arg) {
    int fd;
    int *pointList;
    int bytes;
    int buffer;
    if((fd = open(arg, O_RDONLY)) < 0){ //check if disk can be read
        perror(arg);
        exit(1);
    } 

    for (int i = 1; i < 5; i++)
    {
        lseek(fd, (i * 134217728), SEEK_SET);
        read(fd, &buffer, 1);
        printf("C: %02X\n", buffer);
    }
}

I am getting an output of

argc : 2 
argv /dev/sdc1 
C: 5500
C: 5500
C: 5500
C: 5500

but also sometimes the number is 5600.

My issue is that I am not sure that I am reading in the bytes correctly, or if I am, why does the output oscillate?

If I am wrong, what should I do in order to fix it? Any help is appreciated.