There seems to be an off-by-one error when assigning a location to an unbound inscription at block 879369.
If we look at the last unbound inscription at block 879368 we see its location as
0000000000000000000000000000000000000000000000000000000000000000:0:74620
However, the first unbound inscription in the next block 879369 reports its location as
0000000000000000000000000000000000000000000000000000000000000000:0:74622
Perhaps I'm missing something but shouldn't that inscription be at unbound offset 746621?