Marketing > Leads (/admin/leads) lists email addresses captured by the Macro Calculator component on your website (Macros module). When that component has Ask Email enabled, visitors who compute their macros can enter their email under the "Get results in your email" form; Sprwt stores the lead, emails them their results (system email "email_client_bmr_widget"), and sets a one-hour cookie so the form is not shown again immediately. The menu entry only appears when the Macros module is active.