Two trackers that are started and saved at the same time will always show the exact same data (provided they are not paused). However, two trackers that are started and saved on different dates will show different data since new trackers do not collect old (historical) data.
For example, if tracker 1 was started on January 1st and tracker 2 was started on January 10th, tracker 2 will not include full data from January 1-10. Only a sample set of data from past dates will be included in the second tracker, resulting in different metrics being shown.
As mentioned on the pricing page, real-time trackers do not include historical data. All historical data needs to be ordered separately through our Historical Reports service, or will be included in trackers if subscribed at the Enterprise level.