[SilasX]

I think you can just take that to mean that the response (around some reasonable window) for the real drug was indistinguishable form the non-drug response window, with the assumption that a previous use of the real drug was too far away to account for the non-drug response.

Yes, that's an assumption you should further clamp down later because of such extraordinary results, but it's not unreasonable to make it, especially since it would be really strange for the earlier real drug to cause all its effectiveness spikes right when the non-drug is taken, and in the same amount as later uses of the real drug.