Why does the number of Customer IDs in the Segment Manager differ from the number of Visitors in Mapp Intelligence?

The number of Customer IDs in the Segment Manager is generally lower than the number of "Visitors" in Intelligence.

The number of Customer IDs in the Segment Manager:

The number of "Visitors" in Mapp Intelligence:

The reasons for that are:

• The Segment Manager output (i.e., the table and the number of users) only contains users whose last visit happened within the analysis period. In contrast, the "Visitors" metric in Mapp Intelligence counts every user who visited the page within the analysis period.
  
  Example:
  Suppose you create an analysis on Jan 31 and choose the period from Jan 10 to Jan 20 as the analysis period. Suppose a user visits the website on Jan 15 (within the analysis period) and Jan 27 (after the analysis period). In that case, his Customer ID is not considered for this Segment Manager analysis because his last visit did not happen within the analysis period.
  
  
• In the Segment Manager, an automatic data cleanup follows distinguished rules. This avoids the accumulation of data that is not relevant. Therefore, particular Customer IDs are not part of the Segment Manager analysis; nevertheless, each corresponding visitor is counted in the "Visitors" metric (as any other visitor). The automatic cleanup rules are described in the Training Chapter URM – User-Data.