This rating shows which people you are likelier to message frequently. Telegram uses this data to populate the 'People' box at the top of the Search section. This rating is also calculated for inline bots so that the app can suggest the bots you are most likely to use in the attachment menu (or when you start a new message with "@"). To delete this data, go to Settings > Privacy & Security and disable 'Suggest Frequent Contacts' (requires Telegram for iOS v.4.8.3 or Telegram for Android v.4.8.10 or higher).