A comment was made above: "The only way it can go up is if one or more that have already received his/her heavenly reward turns bad and has to be replaced."
Not so. There is another explanation. [Disclaimer: I do not believe this.]
The replacement of an "unfaithful, formerly anointed" individual need not be immediate, but rather, take place after the passage of some time (perhaps several years). Thus, the number of recognized anointed members of the "Remnant" will fall both because of death AND upon their defection from the "one, true Faith" []. Accordingly, it could be (but need not appear as) a one-for-one replacement because the cumulative defection of not-yet-replaced Evil Slaves could take place over several years, followed by a total replacement in a SINGLE year. If the number of recognized replacements exceeds the number of those who have died faithful since the previous Memorial, the total number of "anointed" will appear to increase. Of course, such an explanation is necessary only if the number 144 000 be literal.