I think we have to assume that the vast majority of house 1 activity on the buy and sell of SPY shares is in fact house 87. As to why they sometimes mark their transactions house 1 and sometimes house 87, I have no idea. All their buying/selling/crossing does not make alot of sense and really in almost a year and a half has seemingly accomplished nothing at all. Perhaps to some with more information this is all a perfectly conceived and executed plan, but to someone watching from the outside, it just looks like a pile of garbage. Not that I'm being critical.