events outside the NLO cuts required

Dear experts,

I am curious about the NLO cuts implementation in MG. e.g., for process "p p > e+ e- j [QCD]",
1. mll_sf cut: the produced events strictly have mll_sf required in the run card
2. pt_ll cut: I required pt_ll to be inside (50,80) in the cuts.f, and I found all the events without additional emission have pt_ll in (50,80), and those events with additional emission have wider pt_ll range. Around 20% of those events (with additional emission) have pt_ll < 50 or pt_ll > 80 and almost all of them have negative weights. I found the answer in https://answers.launchpad.net/mg5amcnlo/+question/403298, it's due to the fact that selections in cuts.f are applied in born level (nexternal=6 for this process in nexternal.inc) and then the real emission will reshuffle the momenta of born level n-body and lead to smaller or large pt_ll.

do I understand correctly. and my question is that what kind of cuts will be affected, e.g., the mll seems not, pt_ll and pt_a (for process with photon) will be affected.

Cheers,
Meng