IFASolar,
I´ll reply in English, but we can continue in Portuguese if you write to the Brazilian support e-mail pvsol@solarize.com.br.
Let me explain your cases:
In the first case, your pv system creates credits between february and august (line "new credit"). In september, october and december, you use these credits to get the "statement of account" down to the minimum consumption that you have defined, 50 kWh per month. In december, there aren´t enough credits, so the statement of account results in 54,94 kWh.
In your second example, the pv system creates credits in several months between march and december. Some months use these credits, but there would be a rest by the end of the year. What would happen in reality? The customer would take the credits from december to the second operational year and use them in january of year two (or even in more months). Following this logic, the "used credit" in the january account is the rest of the first year.
Did I explain it clearly?
Regards,
Hans