diff --git a/workflow-style.qmd b/workflow-style.qmd
index 6061732..88167a3 100644
--- a/workflow-style.qmd
+++ b/workflow-style.qmd
@@ -93,9 +93,11 @@ mean (x ,na.rm=TRUE)
 ```
 
 It's OK to add extra spaces if it improves alignment.
-For example, if you're creating multiple variables in `mutate()`, you might want to add spaces so that all the `=` line up.
+For example, if you're creating multiple variables in `mutate()`, you might want to add spaces so that all the `=` line up.[^workflow-style-1]
 This makes it easier to skim the code.
 
+[^workflow-style-1]: Since `dep_time` is in `HMM` or `HHMM` fomat, we use integer division (`%/%`) to get hour and remainder (also known as modulo, `%%`) to get minute.
+
 ```{r}
 #| eval: false