I have been opening a new history file for each month - I assume you mean the .dat file. It is this file which seems to carry over the total rainfall figure from the previous month. If you are trying to do the same as me - create a file for each month - and you do not have my problem could you tell me the sequence of events you go through please and then I can try it and see if it makes a difference?
If I remember correctly I have been zeroing out the counters on the WS2300, by using the Heavyweather application interface, and not by pressing buttons on the console. I then change the History File by pressing the box at the bottom left of the screen and it then enters the first line of the new data (straight away) - this has the old total rainfall figure in it and just keeps on getting incremented even though the WS2300 shows the accurate total rainfall figure on the LCD display. I'm sure there is some subtle little point I'm missing here, but its eluding me