DOC: fix docstring for pct_change (#53335)

* DOC: fix docstring for .pct_change

* DOC: fix docstring for .pct_change

* DOC: change to comply with black code formatter

Author: gustavovargas

pandas/core/generic.py

@@ -11133,12 +11133,19 @@ def pct_change(
         **kwargs,
     ) -> Self:
         """
-        Percentage change between the current and a prior element.
+        Fractional change between the current and a prior element.
 
-        Computes the percentage change from the immediately previous row by
-        default. This is useful in comparing the percentage of change in a time
+        Computes the fractional change from the immediately previous row by
+        default. This is useful in comparing the fraction of change in a time
         series of elements.
 
+        .. note::
+
+            Despite the name of this method, it calculates fractional change
+            (also known as per unit change or relative change) and not
+            percentage change. If you need the percentage change, multiply
+            these values by 100.
+
         Parameters
         ----------
         periods : int, default 1