Since I was recently checking calibration on my VP2...
This is only for the VP2 console, but I would expect something similar on other Davis consoles...
You can clear the day's rain total by using the cursor keys to select the rain item, then pressing the "2nd" key, and then holding the "clear" key until the rain display data stops blinking and it goes to zero...
If you've downloaded the data into Weatherlink, you can "browse station data", double click on the row of data that contains the rain you want to correct, and a window will pop up allowing you to edit most of the items on that row of data...
I strongly suggest you read the manual for the WMII, and Weatherlink to make sure this will work for you!