I skipped over your message because i4 = 4 integers = 64 bytes, because each 'i' or int is 16 bytes long, there for telling the unpack function to do i4 is telling it to read 4 sixteen byte segments giving you the total of 64 bytes read. Although I did read the answer part, and it just did not compute as the right answer because of the first part.
vB 4.0.1 is out, 4.0.2 should be out in a fortnight, and we are using the latest 3.8.4 branch, just behind by a few patch levels.