Crosstab in Webi Report with 13 months and Totals for 12 months

I have a Crosstab in Webi Report and There should be last 13 months showing. The totals should only be for the last 12, but for example, the March report will have March 2015 – March 2016. The totals would only include April 2015 – March 2016.(see attachment) How would I Limit to 13 months ? And How would I get totals for 12 months only?