The Gen 3 computer has no way to use any of the Gen 4 data outside the 0-80 (400-480) cells, so yeah, it just goes unused. It can't operate in those conditions anyway. If ti goes outside the range of the table it carries on using data from the last used cell (like when in boost, which the table can't account for).
The source data you need is from a late Gen 4, with slightly different tables than the sample 2007 file I posted. But the process is the same. Paste in the cells that line up, interpolate between the filled cells across the ones left empty. It's tedious and a lot of work.
Here's another E40 file that already has the 12613412 data in it. Slight difference between a P59 but the differences are obvious and not hard to figure out what to do.
Flex Fuel Injectors in E40 - 12613412 DSteck.hpt