Update index.md

files/en-us/web/javascript/reference/global_objects/temporal/plainyearmonth/plainyearmonth/index.md

@@ -33,14 +33,12 @@ new Temporal.PlainYearMonth(year, month, calendar, referenceDay)
 - `calendar` {{optional_inline}}
   - : A string representing the [calendar](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Temporal#calendars) to use. Note that irrespective of the `calendar`, the `year`, `month`, and `referenceDay` must be in the ISO 8601 calendar system. Defaults to `"iso8601"`.
 - `referenceDay`
-  - : A number, truncated to an integer, representing the day of the month in the ISO calendar system. Defaults to `1`.
+  - : A number, truncated to an integer, representing the day of the month in the ISO calendar system. Defaults to `1`. The same ISO year-month can represent different months on different days with non-ISO calendars. For example, the days 2021-07-01 and 2021-07-31 may fall in different months in a non-Gregorian calendar, and just specifying "2021-07" is insufficient to unambiguously determine a month in the target calendar. Therefore, you virtually always want to specify a `referenceDay` when using a non-ISO calendar.
 
 ### Return value
 
 A new `Temporal.PlainYearMonth` object, representing the year-month of the date specified by `year`, `month`, and `referenceDay` (in the ISO calendar), interpreted in the calendar system specified by `calendar`.
 
-The same ISO year-month can represent different months on different days with non-ISO calendars. For example, the days 2021-07-01 and 2021-07-31 may fall in different months in a non-Gregorian calendar, and just specifying "2021-07" is insufficient to unambiguously determine a month in the target calendar. Therefore, you virtually always want to specify a `referenceDay` when using a non-ISO calendar.
-
 ### Exceptions
 
 - {{jsxref("TypeError")}}