DFR0534 does not play all files,

I try to play different mp3 und wav Files.

I have Files 01.MP3 to 09.MP3 and 10.wav to 16.wav as it is by default.
When I play a sound using the sample code from the wiki and call play(07), the File 14.wav

Serial.println("Play 07"); // plays 14 instead of 7
play(0x07); //Play the specified audio:0x01-file0001
delay(2000);

I send the Command: AA 07 02 00 07 BA using the function:

void play(unsigned char Track)
{
unsigned char play[6] = {0xAA,0x07,0x02,0x00,Track,Track+0xB3};
Serial1.write(play,6);
}

PS: why do I have to Add 0xB3 to the Track Number? What stands SM for? in the Command
Command: AA 07 02 Upper-Byte Lower-Byte SM