Last Mile test data is collected from Peers all across the globe. If you want a transaction to run in a specific region of the world, you can assign the appropriate Peer Population to it.
In addition to the performance and availability metrics for the test, the Dynatrace Portal collects the test's time (time stamp) and the node from which the test ran.
Last Mile tests are run only from the Peer Populations currently assigned to it. However, when a test's configuration is modified to remove a Peer Population, the test data collected prior to the change still includes the removed Peer Population. Because of this, if the time period charted includes data collected before a Peer Population was removed, the removed Peer Population will be included in the chart. Data will be presented for removed Peer Populations up until the time that they were removed from the test.
For instructions on removing a Peer Population from a test, see Last Mile test settings or Private Last Mile test settings in the documentation.