It's not a question of whether you'll be airborne by the last third of the runway. If you're airborne, you won't need to see anything!
The question is, if you had an RTO just before V1 could you see enough to stop within the first 2/3 of the runway? If yes, then you can disregard the last RVR value as it's not relevant to your takeoff. It won't matter if you can't see two feet in front of you for the last third of the runway as you'll have stopped by then anyway.
For that matter, I suppose you could disregard the middle RVR value as well if your ASDR was somehow shorter than 1/3 of the runway length?