The answer is because we are counting unique visitors over a any given time period, in other words:
The sum of Unique Visitors per DAY is not the same as Unique Visitors per MONTH.
A visitor is calculated as a unique IP (*) over the period you are looking. So, if there are 100 unique visitors in one day, and 50 unique visitors the next day, but 10 people visited on both days, the total number of unique visitors for this 2 day period is 140 unique visitors, not 150.
Get it ? It all depends on the date range.
So, in Logaholic, when you look at the Visitors per month report, you are looking at the UNIQUE number of visitors over the entire month.
When looking at the Visitors per day report, the numbers are unique per day and the total sum is not a unique count.
* NB: There are several ways to count uniques visitors. In Logaholic you can choose between these industry standard methods for identifying and counting unique visitors:
- IP Address or,
- IP Address / Useragent combination or,
- Visitor Cookie
You can select your preferred method on the Advanced tab in the profile settings. The default setting is IP/Agent combination.