diff --git a/docs/collector.os.md b/docs/collector.os.md
index 8bbcd66a..a262cad6 100644
--- a/docs/collector.os.md
+++ b/docs/collector.os.md
@@ -44,7 +44,7 @@ windows_os_timezone{timezone != "UTC"}
 
 Show memory usage for instance (%)
 ```
-100-(windows_os_physical_memory_free_bytes{instance="localhost"} / windows_cs_physical_memory_bytes{instance="localhost"})*100
+100 - 100 * windows_os_physical_memory_free_bytes{instance="localhost"} / windows_cs_physical_memory_bytes{instance="localhost"}
 ```
 
 ## Alerting examples