I truly had no idea. I'll be trying that tomorrow.
Every retrograde burn I planned missed that threshold, sometimes by as little as 10k. Is there an ideal thrust direction for de-orbiting from a circular LKO?
I got Jeb into a stable LKO for the first time. Now he's stuck up there because I only left him 58m/s of dV for a re-entry burn. But hey, 0.0060 eccentricity at 178.5km/184.9km!