The problem I am trying to answer is as follows:
1) I have a stack of parcels in my house.
2) Each day, the post may bring more parcels and/or I may send parcels away.
3) At the end of the day my wife returns home and counts the number of parcels in the house, but she has no direct knowledge of how many parcels were received or sent.
4) A reduced number of parcels observed by my wife may be the result of parcels only having been sent that day, OR of a larger number of parcels having been sent than were received.
5) An increased number of parcels observed by my wife may be the result of parcels only having been received that day, OR of a larger number of parcels having been received than were sent.
6) The number of parcels stored at my house each night may increase or decrease over time.
Is there a way for my wife to estimate the number of parcels that I send each day?
It does not appear so. Suppose, for instance, that every day she counts $n$ parcels. This is consistent with your sending and receiving $k$ parcels per day for any non-negative integer $k$.