Hope answering in english is ok:
where do the values for Stock Inicial come from? Do you calculate them in the chart or do you get them from a field? I am wondering, because Ene 2011 is set to 97,764, where does this value come from?
If you need to calculate the Initial stock values yourself, you could maybe use chart inter record functions, like before([Stock Final]) in your case to retrieve the previous month Final stock, probably adding a total to enable "jumping over year bounderies".
= before(total [Stock Final])
as expression for Stock Inicial.
Hope this helps,