diff --git a/journal/logbook_gustavo.md b/journal/logbook_gustavo.md
index 4463e417db4cc2cfd78270995233bf9f691efe0e..8a1a4c11534a0f37897189c7404c38c4ad432603 100644
--- a/journal/logbook_gustavo.md
+++ b/journal/logbook_gustavo.md
@@ -52,6 +52,14 @@ Once the Git issue was resolved, I was able to finish the task without further p
 
 ### Difficulties encountered
 
+- For exercise 1, an error was found in the line:
+
+`sorted_data['inc'].plot()`
+
+- This happened because the 'inc' data were of type object. To fix this, a line of code was added before to convert the data to numeric:
+
+`sorted_data['inc'] = pd.to_numeric(sorted_data['inc'])`
+
 - For exercise 3.2, there was a problem in data processing because one year had 38 weeks.
 The following change was made to the code: