The rightmost column shows the RNG value behind the item drop. On a lag frame, the RNG advances, as well as the "always running" timer, but the lagged timer doesn't advance. So overall, the column will advance upward, but its values also increment (
lag timer subtracts from the calculated RNG value for the item drop).
If you see a greyed out 49, 99, 149, 199, or 249, a lag frame will turn that into a 50, 100, 150, 200, or 250. According to my notes, that should get you a big weapon refill, along with one more lag increment. Two more lag increments, and it becomes an extra life instead. My script will recolor things for the changed values.
Since numbers change as well as move, I may want an aesthetic change to the script. Namely, some kind of visual marker every 5th frame or so. Should help the eyes track a specific number you're thinking about.
Lag is a pretty major factor, since just three of them can go from "no item drop" to "you just skipped the big weapon refill." It's not the only effect -- I believe some enemies end up affecting the RNG as well, so if something "thinks" just before your kill drops an item (
by "just before", I mean 16 or fewer frames), that can mess up the RNG for the item drop, too. Destroying two enemies close together can also tweak the RNG like this.
Anyway, now I'm thinking about an adjustment to the script. Give me a moment, and I'll have a new one up. This is to have markers every 5th frame, just to help track which frame that RNG value is coming up on.
EDIT:
User movie #33508220465369883
A bit different from what I thought, actually. Lag frames might not advance the RNG on the same frame of lag, but regardless, one timer does still advance while the other doesn't, and this shifts the calculated RNG up by one in most cases. Regardless, here's the updated script that should tell you when every 5th frame happens, assuming the RNG shifts every time.