update burndown_charts base_number -1

app/controllers/api/pm/sprint_issues_controller.rb

@@ -24,7 +24,7 @@ class Api::Pm::SprintIssuesController < Api::Pm::BaseController
       e_time = start_time + x
       completed = curren_issues[[5,e_time]].to_i + curren_issues[[3, e_time]].to_i - @issues.where(pm_issue_type: 3, status_id: 3).size
       total_count = total_count - completed
-      data << {time: e_time, undone: total_count, completed:completed, base_number: (cardinality * (time_count - x)).to_f.round(2)}
+      data << {time: e_time, undone: total_count, completed:completed, base_number: (cardinality * (time_count - x - 1)).to_f.round(2)}
     end
     render_ok(data: data)
   end