Index: log4j-core/src/main/java/org/apache/logging/log4j/core/appender/rolling/RollingFileManager.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- log4j-core/src/main/java/org/apache/logging/log4j/core/appender/rolling/RollingFileManager.java	(date 1533309554000)
+++ log4j-core/src/main/java/org/apache/logging/log4j/core/appender/rolling/RollingFileManager.java	(date 1540326217269)
@@ -151,6 +151,13 @@
             if (triggeringPolicy instanceof LifeCycle) {
                 ((LifeCycle) triggeringPolicy).start();
             }
+            if (rolloverStrategy instanceof DirectFileRolloverStrategy) {
+                // LOG4J2-2485: Initialize size from the most recently written file.
+                File file = new File(getFileName());
+                if (file.exists()) {
+                    size = file.length();
+                }
+            }
         }
     }