Billogram provides you with statistics for the number of invoices sent, cash flows, revenues and similar. These statistics are dynamic, as opposed to your bookkeeping reports, and can be changed to match you billing practices. For example, when you credit an invoice from January in March, the statistics for January will be corrected to reflect this change.
Note that you should not use these statistic for your bookkeeping since they are dynamic. The statistic may differ from your bookkeeping report and should be used to gain an overview of your billing for the period you choose.