How do I keep a constant calculation of the number of leads received over a set period of time? Currently I have noticed that each time a report is pulled on an historical period of time the report output changes if the leads between report requests have been converted.

This means that historical comparisons of leads received and converted can not be calculated accurately. Please advise if I am looking at the incorrect leads report or if there is a specific selection which will allocate a count record of each lead for a set period of time?

Thanking you