Statistics 24hours Unique Visitors

I’ve been a Cloudflare member for a while now and it strikes my mind how I am supposed to read the statistics on Cloudflare. It seems to be that Unique Visitors have a flaw because it says within 24hours there is supposed to have been:
557 Unique Visitors
But when calculating all the values together from the graph on a calculator the number says:
2.65K Unique Visitors along a 24hours period.
Another site of mine over a period of 24hours is saying:
3.71K Unique Visitors
But with calulator adding up the graph numbers over a period of 24hours it says::
24.25K Unique Visitors

How come? Is it necessary to use calculator all the time when looking into the statistics or could something be done to improve the read-outs to be more accurate? And where do I suggest such change? The other read-outs (Total Requests, Percent Cached etc.) seems to be accurate considering the numbers vs. addition on a calculator from the graph.

Thank you for your time reading.

Best wishes,
Kim Jacobsen

Unique visitors are calculated in the increments of the graphing periods and then deduplicated when presenting the total for the queried total timeframe.