update trend statuses threshold

app/models/trends/statuses.rb

@@ -7,12 +7,12 @@ class Trends::Statuses < Trends::Base
     threshold: 10,
     review_threshold: 10,
     score_halflife: 12.hours.freeze,
-    decay_threshold: 1.8,
+    decay_threshold: 0.007,
     expected: 5.0,
-    # (11 - 5)^2 / 5 * 0.5^2 = 1.8
-    # so a status with 11 favourites can stay 24hours
-    # 17 favourites, 2 days
-    # 29 favourites, 3 days
+    # (11 - 5)^2 / 5 * 0.5^10 = 0.00703125
+    # so a status with 11 favourites can stay 5 days
+    # 17 favourites, 6 days
+    # 29 favourites, 1 week
   }
 
   class Query < Trends::Query