When you are working with large data sets in graphs, TARGIT will operate with a default upper limit of data points. If the limit is exceeded, you will not see all data points, but rather just a sample of the data.
In most cases this works well to improve the time it takes to present representative data.
In some cases, however, it is necessary to see more data points - or even all of them - albeit this may be at the cost of poorer performance. You can override the Data Point Limit in the Charts dialog.
One example is the ability to see outliers in a huge data set: