A Little Help from my Friends

I'm letting you and m_tarler​ deal with most of the substance of your inquiry. I do have one observation and question based on some prior experience of my own, which I'll describe. What caught my eye was the notion that some previous month's data does change but "isn't allowed to." 

First, my prior experience and why this "does" but "isn't allowed" caught my eye. I had responsibility at one point some 30 years ago, before I retired, to report monthly headcount data to top management of a major corporation. The senior VP of human resources had "a thing" about consistency from month to month. If we reported a headcount of 1,234 for a given location for the end of June, then THAT PRECISE NUMBER had to be reported in July's headcount report, PERIOD! The trouble was that the reality wasn't caught in a timely basis; transactions for June--hirings, transfers, terminations, whatever--might be entered into the database early in July reflecting an actual change that had happened in June. So though 1,234 was an accurate reading of the database when first reported, it was no longer accurate for June by the time the next month rolled around.

I was more of a stickler for let's report actual facts, even if doing so requires slight adjustments to prior reports. That can be explained and understood--and, significantly, be less troublesome in the long run--building fiction on fiction in a never ending attempt to try to incorporate actual current history into an increasingly false picture of past reality.

Now, maybe that kind of "hanging on to a past number because once reported, we're stuck with it" mindset is not what you're dealing with. Maybe your reality really does freeze, once reported. But if you are in a situation like I describe, maybe dealing with volumes of inventory, or counts of sales calls--rather than headcount of employees--if you are being asked to juggle numbers in a way that really isn't accurate, because of delays in reports of transactions that affect previous months' numbers--I would encourage appealing to reason via a clear explanation of why and how last month's numbers NEED to be modified from time-to-time in order to be truly accurate.