Please ensure that Controller Pak functions such as displaying note names, deleting notes, and so on are performed properly, even when data other than null (0x00) data are detected in the 2nd, 3rd, and 4th bytes (the reserved region) of the note extension.
According to the N64 Programming Manual, the 2nd, 3rd, and 4th bytes (the reserved region of the note extension) are supposed to be 0x00 in the game note for a Controller Pak. However, there is a possibility that incorrect data might be written to the reserved region of the Controller Pak due to corrupted data or some other problem. Therefore, it is possible that the routine written on condition that there are 0x00 data in the reserved region might not be performed properly.
Please see the SI Device section of the N64 Programming Manual, "3.3.2 Create a new game note." for additional information about the game note.