diff --git a/docs/external_usb_ssd_UAS.md b/docs/external_usb_ssd_UAS.md
index 46409ab..100e59d 100644
--- a/docs/external_usb_ssd_UAS.md
+++ b/docs/external_usb_ssd_UAS.md
@@ -47,7 +47,7 @@ Then reboot, the TRIM will be **enabled**.
 
 #### 3.Fstrim the SSD device
 
-1st time, run "**fstrim -v /**" successfull:
+1'st time, run "**fstrim -v /**" successfull:
 
 ```
 $ sudo fstrim -v /