How to correct/recalculate the monthly rain value?

I found this thread:
http://discourse.weather-watch.com/t/27619

Could be useful in solving my problem but the WD version I’m running (latest release) miss the “new monthly total rain” field and the relative button “correct the monthly total rain”.

Any help in finding them much appreciated!

And last thing discovered, in the attempt to correct the first month with error (Feb 2007), I see that 22007lg.txt report correct rain value but 22007lgten.txt report lot’s of error about rain value, I believe the problem come from this log file.